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2024-10-22KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()Breno Leitao1-2/+3
commit 49f683b41f28918df3e51ddc0d928cb2e934ccdb upstream. Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the loads and stores are atomic. In the extremely unlikely scenario the compiler tears the stores, it's theoretically possible for KVM to attempt to get a vCPU using an out-of-bounds index, e.g. if the write is split into multiple 8-bit stores, and is paired with a 32-bit load on a VM with 257 vCPUs: CPU0 CPU1 last_boosted_vcpu = 0xff; (last_boosted_vcpu = 0x100) last_boosted_vcpu[15:8] = 0x01; i = (last_boosted_vcpu = 0x1ff) last_boosted_vcpu[7:0] = 0x00; vcpu = kvm->vcpu_array[0x1ff]; As detected by KCSAN: BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm] write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) value changed: 0x00000012 -> 0x00000000 Fixes: 217ece6129f2 ("KVM: use yield_to instead of sleep in kvm_vcpu_on_spin") Cc: stable@vger.kernel.org Signed-off-by: Breno Leitao <leitao@debian.org> Link: https://lore.kernel.org/r/20240510092353.2261824-1-leitao@debian.org Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-04-10KVM: Always flush async #PF workqueue when vCPU is being destroyedSean Christopherson1-5/+26
[ Upstream commit 3d75b8aa5c29058a512db29da7cbee8052724157 ] Always flush the per-vCPU async #PF workqueue when a vCPU is clearing its completion queue, e.g. when a VM and all its vCPUs is being destroyed. KVM must ensure that none of its workqueue callbacks is running when the last reference to the KVM _module_ is put. Gifting a reference to the associated VM prevents the workqueue callback from dereferencing freed vCPU/VM memory, but does not prevent the KVM module from being unloaded before the callback completes. Drop the misguided VM refcount gifting, as calling kvm_put_kvm() from async_pf_execute() if kvm_put_kvm() flushes the async #PF workqueue will result in deadlock. async_pf_execute() can't return until kvm_put_kvm() finishes, and kvm_put_kvm() can't return until async_pf_execute() finishes: WARNING: CPU: 8 PID: 251 at virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm] Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Workqueue: events async_pf_execute [kvm] RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm] Call Trace: <TASK> async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 </TASK> ---[ end trace 0000000000000000 ]--- INFO: task kworker/8:1:251 blocked for more than 120 seconds. Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/8:1 state:D stack:0 pid:251 ppid:2 flags:0x00004000 Workqueue: events async_pf_execute [kvm] Call Trace: <TASK> __schedule+0x33f/0xa40 schedule+0x53/0xc0 schedule_timeout+0x12a/0x140 __wait_for_common+0x8d/0x1d0 __flush_work.isra.0+0x19f/0x2c0 kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm] kvm_arch_destroy_vm+0x78/0x1b0 [kvm] kvm_put_kvm+0x1c1/0x320 [kvm] async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 </TASK> If kvm_clear_async_pf_completion_queue() actually flushes the workqueue, then there's no need to gift async_pf_execute() a reference because all invocations of async_pf_execute() will be forced to complete before the vCPU and its VM are destroyed/freed. And that in turn fixes the module unloading bug as __fput() won't do module_put() on the last vCPU reference until the vCPU has been freed, e.g. if closing the vCPU file also puts the last reference to the KVM module. Note that kvm_check_async_pf_completion() may also take the work item off the completion queue and so also needs to flush the work queue, as the work will not be seen by kvm_clear_async_pf_completion_queue(). Waiting on the workqueue could theoretically delay a vCPU due to waiting for the work to complete, but that's a very, very small chance, and likely a very small delay. kvm_arch_async_page_present_queued() unconditionally makes a new request, i.e. will effectively delay entering the guest, so the remaining work is really just: trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm); and mmput() can't drop the last reference to the page tables if the vCPU is still alive, i.e. the vCPU won't get stuck tearing down page tables. Add a helper to do the flushing, specifically to deal with "wakeup all" work items, as they aren't actually work items, i.e. are never placed in a workqueue. Trying to flush a bogus workqueue entry rightly makes __flush_work() complain (kudos to whoever added that sanity check). Note, commit 5f6de5cbebee ("KVM: Prevent module exit until all VMs are freed") *tried* to fix the module refcounting issue by having VMs grab a reference to the module, but that only made the bug slightly harder to hit as it gave async_pf_execute() a bit more time to complete before the KVM module could be unloaded. Fixes: af585b921e5d ("KVM: Halt vcpu if page it tries to access is swapped out") Cc: stable@vger.kernel.org Cc: David Matlack <dmatlack@google.com> Reviewed-by: Xu Yilun <yilun.xu@intel.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Link: https://lore.kernel.org/r/20240110011533.503302-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-08-03KVM: Grab a reference to KVM for VM and vCPU stats file descriptorsSean Christopherson1-0/+24
commit eed3013faa401aae662398709410a59bb0646e32 upstream. Grab a reference to KVM prior to installing VM and vCPU stats file descriptors to ensure the underlying VM and vCPU objects are not freed until the last reference to any and all stats fds are dropped. Note, the stats paths manually invoke fd_install() and so don't need to grab a reference before creating the file. Fixes: ce55c049459c ("KVM: stats: Support binary stats retrieval for a VCPU") Fixes: fcfe1baeddbf ("KVM: stats: Support binary stats retrieval for a VM") Reported-by: Zheng Zhang <zheng.zhang@email.ucr.edu> Closes: https://lore.kernel.org/all/CAC_GQSr3xzZaeZt85k_RCBd5kfiOve8qXo7a81Cq53LuVQ5r=Q@mail.gmail.com Cc: stable@vger.kernel.org Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Message-Id: <20230711230131.648752-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-06-28KVM: Avoid illegal stage2 mapping on invalid memory slotGavin Shan1-1/+19
commit 2230f9e1171a2e9731422a14d1bbc313c0b719d1 upstream. We run into guest hang in edk2 firmware when KSM is kept as running on the host. The edk2 firmware is waiting for status 0x80 from QEMU's pflash device (TYPE_PFLASH_CFI01) during the operation of sector erasing or buffered write. The status is returned by reading the memory region of the pflash device and the read request should have been forwarded to QEMU and emulated by it. Unfortunately, the read request is covered by an illegal stage2 mapping when the guest hang issue occurs. The read request is completed with QEMU bypassed and wrong status is fetched. The edk2 firmware runs into an infinite loop with the wrong status. The illegal stage2 mapping is populated due to same page sharing by KSM at (C) even the associated memory slot has been marked as invalid at (B) when the memory slot is requested to be deleted. It's notable that the active and inactive memory slots can't be swapped when we're in the middle of kvm_mmu_notifier_change_pte() because kvm->mn_active_invalidate_count is elevated, and kvm_swap_active_memslots() will busy loop until it reaches to zero again. Besides, the swapping from the active to the inactive memory slots is also avoided by holding &kvm->srcu in __kvm_handle_hva_range(), corresponding to synchronize_srcu_expedited() in kvm_swap_active_memslots(). CPU-A CPU-B ----- ----- ioctl(kvm_fd, KVM_SET_USER_MEMORY_REGION) kvm_vm_ioctl_set_memory_region kvm_set_memory_region __kvm_set_memory_region kvm_set_memslot(kvm, old, NULL, KVM_MR_DELETE) kvm_invalidate_memslot kvm_copy_memslot kvm_replace_memslot kvm_swap_active_memslots (A) kvm_arch_flush_shadow_memslot (B) same page sharing by KSM kvm_mmu_notifier_invalidate_range_start : kvm_mmu_notifier_change_pte kvm_handle_hva_range __kvm_handle_hva_range kvm_set_spte_gfn (C) : kvm_mmu_notifier_invalidate_range_end Fix the issue by skipping the invalid memory slot at (C) to avoid the illegal stage2 mapping so that the read request for the pflash's status is forwarded to QEMU and emulated by it. In this way, the correct pflash's status can be returned from QEMU to break the infinite loop in the edk2 firmware. We tried a git-bisect and the first problematic commit is cd4c71835228 (" KVM: arm64: Convert to the gfn-based MMU notifier callbacks"). With this, clean_dcache_guest_page() is called after the memory slots are iterated in kvm_mmu_notifier_change_pte(). clean_dcache_guest_page() is called before the iteration on the memory slots before this commit. This change literally enlarges the racy window between kvm_mmu_notifier_change_pte() and memory slot removal so that we're able to reproduce the issue in a practical test case. However, the issue exists since commit d5d8184d35c9 ("KVM: ARM: Memory virtualization setup"). Cc: stable@vger.kernel.org # v3.9+ Fixes: d5d8184d35c9 ("KVM: ARM: Memory virtualization setup") Reported-by: Shuai Hu <hshuai@redhat.com> Reported-by: Zhenyu Zhang <zhenyzha@redhat.com> Signed-off-by: Gavin Shan <gshan@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Oliver Upton <oliver.upton@linux.dev> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Shaoqin Huang <shahuang@redhat.com> Message-Id: <20230615054259.14911-1-gshan@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-03-17KVM: fix memoryleak in kvm_init()Miaohe Lin1-3/+2
commit 5a2a961be2ad6a16eb388a80442443b353c11d16 upstream. When alloc_cpumask_var_node() fails for a certain cpu, there might be some allocated cpumasks for percpu cpu_kick_mask. We should free these cpumasks or memoryleak will occur. Fixes: baff59ccdc65 ("KVM: Pre-allocate cpumasks for kvm_make_all_cpus_request_except()") Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Link: https://lore.kernel.org/r/20220823063414.59778-1-linmiaohe@huawei.com Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-03-17KVM: Register /dev/kvm as the _very_ last thing during initializationSean Christopherson1-9/+22
[ Upstream commit 2b01281273738bf2d6551da48d65db2df3f28998 ] Register /dev/kvm, i.e. expose KVM to userspace, only after all other setup has completed. Once /dev/kvm is exposed, userspace can start invoking KVM ioctls, creating VMs, etc... If userspace creates a VM before KVM is done with its configuration, bad things may happen, e.g. KVM will fail to properly migrate vCPU state if a VM is created before KVM has registered preemption notifiers. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20221130230934.1014142-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-03-17KVM: Pre-allocate cpumasks for kvm_make_all_cpus_request_except()Vitaly Kuznetsov1-6/+23
[ Upstream commit baff59ccdc657d290be51b95b38ebe5de40036b4 ] Allocating cpumask dynamically in zalloc_cpumask_var() is not ideal. Allocation is somewhat slow and can (in theory and when CPUMASK_OFFSTACK) fail. kvm_make_all_cpus_request_except() already disables preemption so we can use pre-allocated per-cpu cpumasks instead. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Reviewed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210903075141.403071-8-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Stable-dep-of: 2b0128127373 ("KVM: Register /dev/kvm as the _very_ last thing during initialization") Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-03-17KVM: Optimize kvm_make_vcpus_request_mask() a bitVitaly Kuznetsov1-35/+53
[ Upstream commit ae0946cd3601752dc58f86d84258e5361e9c8cd4 ] Iterating over set bits in 'vcpu_bitmap' should be faster than going through all vCPUs, especially when just a few bits are set. Drop kvm_make_vcpus_request_mask() call from kvm_make_all_cpus_request_except() to avoid handling the special case when 'vcpu_bitmap' is NULL, move the code to kvm_make_all_cpus_request_except() itself. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Reviewed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210903075141.403071-5-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Stable-dep-of: 2b0128127373 ("KVM: Register /dev/kvm as the _very_ last thing during initialization") Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-03-10KVM: Destroy target device if coalesced MMIO unregistration failsSean Christopherson1-3/+5
commit b1cb1fac22abf102ffeb29dd3eeca208a3869d54 upstream. Destroy and free the target coalesced MMIO device if unregistering said device fails. As clearly noted in the code, kvm_io_bus_unregister_dev() does not destroy the target device. BUG: memory leak unreferenced object 0xffff888112a54880 (size 64): comm "syz-executor.2", pid 5258, jiffies 4297861402 (age 14.129s) hex dump (first 32 bytes): 38 c7 67 15 00 c9 ff ff 38 c7 67 15 00 c9 ff ff 8.g.....8.g..... e0 c7 e1 83 ff ff ff ff 00 30 67 15 00 c9 ff ff .........0g..... backtrace: [<0000000006995a8a>] kmalloc include/linux/slab.h:556 [inline] [<0000000006995a8a>] kzalloc include/linux/slab.h:690 [inline] [<0000000006995a8a>] kvm_vm_ioctl_register_coalesced_mmio+0x8e/0x3d0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:150 [<00000000022550c2>] kvm_vm_ioctl+0x47d/0x1600 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3323 [<000000008a75102f>] vfs_ioctl fs/ioctl.c:46 [inline] [<000000008a75102f>] file_ioctl fs/ioctl.c:509 [inline] [<000000008a75102f>] do_vfs_ioctl+0xbab/0x1160 fs/ioctl.c:696 [<0000000080e3f669>] ksys_ioctl+0x76/0xa0 fs/ioctl.c:713 [<0000000059ef4888>] __do_sys_ioctl fs/ioctl.c:720 [inline] [<0000000059ef4888>] __se_sys_ioctl fs/ioctl.c:718 [inline] [<0000000059ef4888>] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718 [<000000006444fa05>] do_syscall_64+0x9f/0x4e0 arch/x86/entry/common.c:290 [<000000009a4ed50b>] entry_SYSCALL_64_after_hwframe+0x49/0xbe BUG: leak checking failed Fixes: 5d3c4c79384a ("KVM: Stop looking for coalesced MMIO zones if the bus is destroyed") Cc: stable@vger.kernel.org Reported-by: 柳菁峰 <liujingfeng@qianxin.com> Reported-by: Michal Luczaj <mhal@rbox.co> Link: https://lore.kernel.org/r/20221219171924.67989-1-seanjc@google.com Link: https://lore.kernel.org/all/20230118220003.1239032-1-mhal@rbox.co Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-10-29kvm: Add support for arch compat vm ioctlsAlexander Graf1-0/+11
commit ed51862f2f57cbce6fed2d4278cfe70a490899fd upstream. We will introduce the first architecture specific compat vm ioctl in the next patch. Add all necessary boilerplate to allow architectures to override compat vm ioctls when necessary. Signed-off-by: Alexander Graf <graf@amazon.com> Message-Id: <20221017184541.2658-2-graf@amazon.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-09-23KVM: SEV: add cache flush to solve SEV cache incoherency issuesMingwei Zhang1-3/+24
commit 683412ccf61294d727ead4a73d97397396e69a6b upstream. Flush the CPU caches when memory is reclaimed from an SEV guest (where reclaim also includes it being unmapped from KVM's memslots). Due to lack of coherency for SEV encrypted memory, failure to flush results in silent data corruption if userspace is malicious/broken and doesn't ensure SEV guest memory is properly pinned and unpinned. Cache coherency is not enforced across the VM boundary in SEV (AMD APM vol.2 Section 15.34.7). Confidential cachelines, generated by confidential VM guests have to be explicitly flushed on the host side. If a memory page containing dirty confidential cachelines was released by VM and reallocated to another user, the cachelines may corrupt the new user at a later time. KVM takes a shortcut by assuming all confidential memory remain pinned until the end of VM lifetime. Therefore, KVM does not flush cache at mmu_notifier invalidation events. Because of this incorrect assumption and the lack of cache flushing, malicous userspace can crash the host kernel: creating a malicious VM and continuously allocates/releases unpinned confidential memory pages when the VM is running. Add cache flush operations to mmu_notifier operations to ensure that any physical memory leaving the guest VM get flushed. In particular, hook mmu_notifier_invalidate_range_start and mmu_notifier_release events and flush cache accordingly. The hook after releasing the mmu lock to avoid contention with other vCPUs. Cc: stable@vger.kernel.org Suggested-by: Sean Christpherson <seanjc@google.com> Reported-by: Mingwei Zhang <mizhang@google.com> Signed-off-by: Mingwei Zhang <mizhang@google.com> Message-Id: <20220421031407.2516575-4-mizhang@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [OP: adjusted KVM_X86_OP_OPTIONAL() -> KVM_X86_OP_NULL, applied kvm_arch_guest_memory_reclaimed() call in kvm_set_memslot()] Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-08-25KVM: Unconditionally get a ref to /dev/kvm module when creating a VMSean Christopherson1-10/+4
commit 405294f29faee5de8c10cb9d4a90e229c2835279 upstream. Unconditionally get a reference to the /dev/kvm module when creating a VM instead of using try_get_module(), which will fail if the module is in the process of being forcefully unloaded. The error handling when try_get_module() fails doesn't properly unwind all that has been done, e.g. doesn't call kvm_arch_pre_destroy_vm() and doesn't remove the VM from the global list. Not removing VMs from the global list tends to be fatal, e.g. leads to use-after-free explosions. The obvious alternative would be to add proper unwinding, but the justification for using try_get_module(), "rmmod --wait", is completely bogus as support for "rmmod --wait", i.e. delete_module() without O_NONBLOCK, was removed by commit 3f2b9c9cdf38 ("module: remove rmmod --wait option.") nearly a decade ago. It's still possible for try_get_module() to fail due to the module dying (more like being killed), as the module will be tagged MODULE_STATE_GOING by "rmmod --force", i.e. delete_module(..., O_TRUNC), but playing nice with forced unloading is an exercise in futility and gives a falsea sense of security. Using try_get_module() only prevents acquiring _new_ references, it doesn't magically put the references held by other VMs, and forced unloading doesn't wait, i.e. "rmmod --force" on KVM is all but guaranteed to cause spectacular fireworks; the window where KVM will fail try_get_module() is tiny compared to the window where KVM is building and running the VM with an elevated module refcount. Addressing KVM's inability to play nice with "rmmod --force" is firmly out-of-scope. Forcefully unloading any module taints kernel (for obvious reasons) _and_ requires the kernel to be built with CONFIG_MODULE_FORCE_UNLOAD=y, which is off by default and comes with the amusing disclaimer that it's "mainly for kernel developers and desperate users". In other words, KVM is free to scoff at bug reports due to using "rmmod --force" while VMs may be running. Fixes: 5f6de5cbebee ("KVM: Prevent module exit until all VMs are freed") Cc: stable@vger.kernel.org Cc: David Matlack <dmatlack@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220816053937.2477106-3-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-08-17KVM: Don't set Accessed/Dirty bits for ZERO_PAGESean Christopherson1-2/+14
[ Upstream commit a1040b0d42acf69bb4f6dbdc54c2dcd78eea1de5 ] Don't set Accessed/Dirty bits for a struct page with PG_reserved set, i.e. don't set A/D bits for the ZERO_PAGE. The ZERO_PAGE (or pages depending on the architecture) should obviously never be written, and similarly there's no point in marking it accessed as the page will never be swapped out or reclaimed. The comment in page-flags.h is quite clear that PG_reserved pages should be managed only by their owner, and strictly following that mandate also simplifies KVM's logic. Fixes: 7df003c85218 ("KVM: fix overflow of zero page refcount with ksm running") Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220429010416.2788472-4-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-07-29KVM: Don't null dereference ops->destroyAlexey Kardashevskiy1-1/+4
commit e8bc2427018826e02add7b0ed0fc625a60390ae5 upstream. A KVM device cleanup happens in either of two callbacks: 1) destroy() which is called when the VM is being destroyed; 2) release() which is called when a device fd is closed. Most KVM devices use 1) but Book3s's interrupt controller KVM devices (XICS, XIVE, XIVE-native) use 2) as they need to close and reopen during the machine execution. The error handling in kvm_ioctl_create_device() assumes destroy() is always defined which leads to NULL dereference as discovered by Syzkaller. This adds a checks for destroy!=NULL and adds a missing release(). This is not changing kvm_destroy_devices() as devices with defined release() should have been removed from the KVM devices list by then. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-07-12KVM: Initialize debugfs_dentry when a VM is created to avoid NULL derefSean Christopherson1-6/+6
[ Upstream commit 5c697c367a66307a5d943c3449421aff2aa3ca4a ] Initialize debugfs_entry to its semi-magical -ENOENT value when the VM is created. KVM's teardown when VM creation fails is kludgy and calls kvm_uevent_notify_change() and kvm_destroy_vm_debugfs() even if KVM never attempted kvm_create_vm_debugfs(). Because debugfs_entry is zero initialized, the IS_ERR() checks pass and KVM derefs a NULL pointer. BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1068b1067 P4D 1068b1067 PUD 1068b0067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 871 Comm: repro Not tainted 5.18.0-rc1+ #825 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:__dentry_path+0x7b/0x130 Call Trace: <TASK> dentry_path_raw+0x42/0x70 kvm_uevent_notify_change.part.0+0x10c/0x200 [kvm] kvm_put_kvm+0x63/0x2b0 [kvm] kvm_dev_ioctl+0x43a/0x920 [kvm] __x64_sys_ioctl+0x83/0xb0 do_syscall_64+0x31/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xae </TASK> Modules linked in: kvm_intel kvm irqbypass Fixes: a44a4cc1c969 ("KVM: Don't create VM debugfs files outside of the VM directory") Cc: stable@vger.kernel.org Cc: Marc Zyngier <maz@kernel.org> Cc: Oliver Upton <oupton@google.com> Reported-by: syzbot+df6fbbd2ee39f21289ef@syzkaller.appspotmail.com Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Oliver Upton <oupton@google.com> Message-Id: <20220415004622.2207751-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-07-12KVM: Don't create VM debugfs files outside of the VM directoryOliver Upton1-2/+8
[ Upstream commit a44a4cc1c969afec97dbb2aedaf6f38eaa6253bb ] Unfortunately, there is no guarantee that KVM was able to instantiate a debugfs directory for a particular VM. To that end, KVM shouldn't even attempt to create new debugfs files in this case. If the specified parent dentry is NULL, debugfs_create_file() will instantiate files at the root of debugfs. For arm64, it is possible to create the vgic-state file outside of a VM directory, the file is not cleaned up when a VM is destroyed. Nonetheless, the corresponding struct kvm is freed when the VM is destroyed. Nip the problem in the bud for all possible errant debugfs file creations by initializing kvm->debugfs_dentry to -ENOENT. In so doing, debugfs_create_file() will fail instead of creating the file in the root directory. Cc: stable@kernel.org Fixes: 929f45e32499 ("kvm: no need to check return value of debugfs_create functions") Signed-off-by: Oliver Upton <oupton@google.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220406235615.1447180-2-oupton@google.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-07-12KVM: use __vcalloc for very large allocationsPaolo Bonzini1-2/+2
[ Upstream commit 37b2a6510a48ca361ced679f92682b7b7d7d0330 ] Allocations whose size is related to the memslot size can be arbitrarily large. Do not use kvzalloc/kvcalloc, as those are limited to "not crazy" sizes that fit in 32 bits. Cc: stable@vger.kernel.org Fixes: 7661809d493b ("mm: don't allow oversized kvmalloc() calls") Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-13KVM: avoid NULL pointer dereference in kvm_dirty_ring_pushPaolo Bonzini1-1/+1
commit 5593473a1e6c743764b08e3b6071cb43b5cfa6c4 upstream. kvm_vcpu_release() will call kvm_dirty_ring_free(), freeing ring->dirty_gfns and setting it to NULL. Afterwards, it calls kvm_arch_vcpu_destroy(). However, if closing the file descriptor races with KVM_RUN in such away that vcpu->arch.st.preempted == 0, the following call stack leads to a NULL pointer dereference in kvm_dirty_run_push(): mark_page_dirty_in_slot+0x192/0x270 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3171 kvm_steal_time_set_preempted arch/x86/kvm/x86.c:4600 [inline] kvm_arch_vcpu_put+0x34e/0x5b0 arch/x86/kvm/x86.c:4618 vcpu_put+0x1b/0x70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:211 vmx_free_vcpu+0xcb/0x130 arch/x86/kvm/vmx/vmx.c:6985 kvm_arch_vcpu_destroy+0x76/0x290 arch/x86/kvm/x86.c:11219 kvm_vcpu_destroy arch/x86/kvm/../../../virt/kvm/kvm_main.c:441 [inline] The fix is to release the dirty page ring after kvm_arch_vcpu_destroy has run. Reported-by: Qiuhao Li <qiuhao@sysec.org> Reported-by: Gaoning Pan <pgn@zju.edu.cn> Reported-by: Yongkang Jia <kangel@zju.edu.cn> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-04-08KVM: Prevent module exit until all VMs are freedDavid Matlack1-0/+13
commit 5f6de5cbebee925a612856fce6f9182bb3eee0db upstream. Tie the lifetime the KVM module to the lifetime of each VM via kvm.users_count. This way anything that grabs a reference to the VM via kvm_get_kvm() cannot accidentally outlive the KVM module. Prior to this commit, the lifetime of the KVM module was tied to the lifetime of /dev/kvm file descriptors, VM file descriptors, and vCPU file descriptors by their respective file_operations "owner" field. This approach is insufficient because references grabbed via kvm_get_kvm() do not prevent closing any of the aforementioned file descriptors. This fixes a long standing theoretical bug in KVM that at least affects async page faults. kvm_setup_async_pf() grabs a reference via kvm_get_kvm(), and drops it in an asynchronous work callback. Nothing prevents the VM file descriptor from being closed and the KVM module from being unloaded before this callback runs. Fixes: af585b921e5d ("KVM: Halt vcpu if page it tries to access is swapped out") Fixes: 3d3aab1b973b ("KVM: set owner of cpu and vm file operations") Cc: stable@vger.kernel.org Suggested-by: Ben Gardon <bgardon@google.com> [ Based on a patch from Ben implemented for Google's kernel. ] Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20220303183328.1499189-2-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-03-16KVM: Fix lockdep false negative during host resumeWanpeng Li1-3/+1
[ Upstream commit 4cb9a998b1ce25fad74a82f5a5c45a4ef40de337 ] I saw the below splatting after the host suspended and resumed. WARNING: CPU: 0 PID: 2943 at kvm/arch/x86/kvm/../../../virt/kvm/kvm_main.c:5531 kvm_resume+0x2c/0x30 [kvm] CPU: 0 PID: 2943 Comm: step_after_susp Tainted: G W IOE 5.17.0-rc3+ #4 RIP: 0010:kvm_resume+0x2c/0x30 [kvm] Call Trace: <TASK> syscore_resume+0x90/0x340 suspend_devices_and_enter+0xaee/0xe90 pm_suspend.cold+0x36b/0x3c2 state_store+0x82/0xf0 kernfs_fop_write_iter+0x1b6/0x260 new_sync_write+0x258/0x370 vfs_write+0x33f/0x510 ksys_write+0xc9/0x160 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae lockdep_is_held() can return -1 when lockdep is disabled which triggers this warning. Let's use lockdep_assert_not_held() which can detect incorrect calls while holding a lock and it also avoids false negatives when lockdep is disabled. Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Message-Id: <1644920142-81249-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-03-08KVM: s390: Ensure kvm_arch_no_poll() is read once when blocking vCPUSean Christopherson1-2/+3
[ Upstream commit 6f390916c4fb359507d9ac4bf1b28a4f8abee5c0 ] Wrap s390's halt_poll_max_steal with READ_ONCE and snapshot the result of kvm_arch_no_poll() in kvm_vcpu_block() to avoid a mostly-theoretical, largely benign bug on s390 where the result of kvm_arch_no_poll() could change due to userspace modifying halt_poll_max_steal while the vCPU is blocking. The bug is largely benign as it will either cause KVM to skip updating halt-polling times (no_poll toggles false=>true) or to update halt-polling times with a slightly flawed block_ns. Note, READ_ONCE is unnecessary in the current code, add it in case the arch hook is ever inlined, and to provide a hint that userspace can change the param at will. Fixes: 8b905d28ee17 ("KVM: s390: provide kvm_arch_no_poll function") Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20211009021236.4122790-4-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-02-16KVM: eventfd: Fix false positive RCU usage warningHou Wenlong1-4/+4
[ Upstream commit 6a0c61703e3a5d67845a4b275e1d9d7bc1b5aad7 ] Fix the following false positive warning: ============================= WARNING: suspicious RCU usage 5.16.0-rc4+ #57 Not tainted ----------------------------- arch/x86/kvm/../../../virt/kvm/eventfd.c:484 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by fc_vcpu 0/330: #0: ffff8884835fc0b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x88/0x6f0 [kvm] #1: ffffc90004c0bb68 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x600/0x1860 [kvm] #2: ffffc90004c0c1d0 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x36/0x180 [kvm] stack backtrace: CPU: 26 PID: 330 Comm: fc_vcpu 0 Not tainted 5.16.0-rc4+ Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x44/0x57 kvm_notify_acked_gsi+0x6b/0x70 [kvm] kvm_notify_acked_irq+0x8d/0x180 [kvm] kvm_ioapic_update_eoi+0x92/0x240 [kvm] kvm_apic_set_eoi_accelerated+0x2a/0xe0 [kvm] handle_apic_eoi_induced+0x3d/0x60 [kvm_intel] vmx_handle_exit+0x19c/0x6a0 [kvm_intel] vcpu_enter_guest+0x66e/0x1860 [kvm] kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm] kvm_vcpu_ioctl+0x38a/0x6f0 [kvm] __x64_sys_ioctl+0x89/0xc0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Since kvm_unregister_irq_ack_notifier() does synchronize_srcu(&kvm->irq_srcu), kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. In fact, kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), making it a false positive warning. So use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu(). Reviewed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com> Message-Id: <f98bac4f5052bad2c26df9ad50f7019e40434512.1643265976.git.houwenlong.hwl@antgroup.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-02-01Revert "KVM: SVM: avoid infinite loop on NPF from bad address"Sean Christopherson1-1/+0
commit 31c25585695abdf03d6160aa6d829e855b256329 upstream. Revert a completely broken check on an "invalid" RIP in SVM's workaround for the DecodeAssists SMAP errata. kvm_vcpu_gfn_to_memslot() obviously expects a gfn, i.e. operates in the guest physical address space, whereas RIP is a virtual (not even linear) address. The "fix" worked for the problematic KVM selftest because the test identity mapped RIP. Fully revert the hack instead of trying to translate RIP to a GPA, as the non-SEV case is now handled earlier, and KVM cannot access guest page tables to translate RIP. This reverts commit e72436bc3a5206f95bb384e741154166ddb3202e. Fixes: e72436bc3a52 ("KVM: SVM: avoid infinite loop on NPF from bad address") Reported-by: Liam Merwick <liam.merwick@oracle.com> Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Message-Id: <20220120010719.711476-3-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-22KVM: downgrade two BUG_ONs to WARN_ON_ONCEPaolo Bonzini1-2/+4
[ Upstream commit 5f25e71e311478f9bb0a8ef49e7d8b95316491d7 ] This is not an unrecoverable situation. Users of kvm_read_guest_offset_cached and kvm_write_guest_offset_cached must expect the read/write to fail, and therefore it is possible to just return early with an error value. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-12-08KVM: Ensure local memslot copies operate on up-to-date arch-specific dataSean Christopherson1-16/+31
commit bda44d844758c70c8dc1478e6fc9c25efa90c5a7 upstream. When modifying memslots, snapshot the "old" memslot and copy it to the "new" memslot's arch data after (re)acquiring slots_arch_lock. x86 can change a memslot's arch data while memslot updates are in-progress so long as it holds slots_arch_lock, thus snapshotting a memslot without holding the lock can result in the consumption of stale data. Fixes: b10a038e84d1 ("KVM: mmu: Add slots_arch_lock for memslot arch fields") Cc: stable@vger.kernel.org Cc: Ben Gardon <bgardon@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20211104002531.1176691-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-08KVM: Disallow user memslot with size that exceeds "unsigned long"Sean Christopherson1-1/+2
commit 6b285a5587506bae084cf9a3ed5aa491d623b91b upstream. Reject userspace memslots whose size exceeds the storage capacity of an "unsigned long". KVM's uAPI takes the size as u64 to support large slots on 64-bit hosts, but does not account for the size being truncated on 32-bit hosts in various flows. The access_ok() check on the userspace virtual address in particular casts the size to "unsigned long" and will check the wrong number of bytes. KVM doesn't actually support slots whose size doesn't fit in an "unsigned long", e.g. KVM's internal kvm_memory_slot.npages is an "unsigned long", not a "u64", and misc arch specific code follows that behavior. Fixes: fa3d315a4ce2 ("KVM: Validate userspace_addr of memslot when registered") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> Message-Id: <20211104002531.1176691-3-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-09-23KVM: Remove tlbs_dirtyLai Jiangshan1-8/+2
There is no user of tlbs_dirty. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-4-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-22KVM: KVM: Use cpumask_available() to check for NULL cpumask when kicking vCPUsSean Christopherson1-3/+15
Check for a NULL cpumask_var_t when kicking multiple vCPUs via cpumask_available(), which performs a !NULL check if and only if cpumasks are configured to be allocated off-stack. This is a meaningless optimization, e.g. avoids a TEST+Jcc and TEST+CMOV on x86, but more importantly helps document that the NULL check is necessary even though all callers pass in a local variable. No functional change intended. Cc: Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20210827092516.1027264-3-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-22KVM: Clean up benign vcpu->cpu data races when kicking vCPUsSean Christopherson1-8/+28
Fix a benign data race reported by syzbot+KCSAN[*] by ensuring vcpu->cpu is read exactly once, and by ensuring the vCPU is booted from guest mode if kvm_arch_vcpu_should_kick() returns true. Fix a similar race in kvm_make_vcpus_request_mask() by ensuring the vCPU is interrupted if kvm_request_needs_ipi() returns true. Reading vcpu->cpu before vcpu->mode (via kvm_arch_vcpu_should_kick() or kvm_request_needs_ipi()) means the target vCPU could get migrated (change vcpu->cpu) and enter !OUTSIDE_GUEST_MODE between reading vcpu->cpud and reading vcpu->mode. If that happens, the kick/IPI will be sent to the old pCPU, not the new pCPU that is now running the vCPU or reading SPTEs. Although failing to kick the vCPU is not exactly ideal, practically speaking it cannot cause a functional issue unless there is also a bug in the caller, and any such bug would exist regardless of kvm_vcpu_kick()'s behavior. The purpose of sending an IPI is purely to get a vCPU into the host (or out of reading SPTEs) so that the vCPU can recognize a change in state, e.g. a KVM_REQ_* request. If vCPU's handling of the state change is required for correctness, KVM must ensure either the vCPU sees the change before entering the guest, or that the sender sees the vCPU as running in guest mode. All architectures handle this by (a) sending the request before calling kvm_vcpu_kick() and (b) checking for requests _after_ setting vcpu->mode. x86's READING_SHADOW_PAGE_TABLES has similar requirements; KVM needs to ensure it kicks and waits for vCPUs that started reading SPTEs _before_ MMU changes were finalized, but any vCPU that starts reading after MMU changes were finalized will see the new state and can continue on uninterrupted. For uses of kvm_vcpu_kick() that are not paired with a KVM_REQ_*, e.g. x86's kvm_arch_sync_dirty_log(), the order of the kick must not be relied upon for functional correctness, e.g. in the dirty log case, userspace cannot assume it has a 100% complete log if vCPUs are still running. All that said, eliminate the benign race since the cost of doing so is an "extra" atomic cmpxchg() in the case where the target vCPU is loaded by the current pCPU or is not loaded at all. I.e. the kick will be skipped due to kvm_vcpu_exiting_guest_mode() seeing a compatible vcpu->mode as opposed to the kick being skipped because of the cpu checks. Keep the "cpu != me" checks even though they appear useless/impossible at first glance. x86 processes guest IPI writes in a fast path that runs in IN_GUEST_MODE, i.e. can call kvm_vcpu_kick() from IN_GUEST_MODE. And calling kvm_vm_bugged()->kvm_make_vcpus_request_mask() from IN_GUEST or READING_SHADOW_PAGE_TABLES is perfectly reasonable. Note, a race with the cpu_online() check in kvm_vcpu_kick() likely persists, e.g. the vCPU could exit guest mode and get offlined between the cpu_online() check and the sending of smp_send_reschedule(). But, the online check appears to exist only to avoid a WARN in x86's native_smp_send_reschedule() that fires if the target CPU is not online. The reschedule WARN exists because CPU offlining takes the CPU out of the scheduling pool, i.e. the WARN is intended to detect the case where the kernel attempts to schedule a task on an offline CPU. The actual sending of the IPI is a non-issue as at worst it will simpy be dropped on the floor. In other words, KVM's usurping of the reschedule IPI could theoretically trigger a WARN if the stars align, but there will be no loss of functionality. [*] https://syzkaller.appspot.com/bug?extid=cd4154e502f43f10808a Cc: Venkatesh Srinivas <venkateshs@google.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Fixes: 97222cc83163 ("KVM: Emulate local APIC in kernel") Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20210827092516.1027264-2-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-22KVM: do not shrink halt_poll_ns below grow_startSergey Senozhatsky1-1/+5
grow_halt_poll_ns() ignores values between 0 and halt_poll_ns_grow_start (10000 by default). However, when we shrink halt_poll_ns we may fall way below halt_poll_ns_grow_start and endup with halt_poll_ns values that don't make a lot of sense: like 1 or 9, or 19. VCPU1 trace (halt_poll_ns_shrink equals 2): VCPU1 grow 10000 VCPU1 shrink 5000 VCPU1 shrink 2500 VCPU1 shrink 1250 VCPU1 shrink 625 VCPU1 shrink 312 VCPU1 shrink 156 VCPU1 shrink 78 VCPU1 shrink 39 VCPU1 shrink 19 VCPU1 shrink 9 VCPU1 shrink 4 Mirror what grow_halt_poll_ns() does and set halt_poll_ns to 0 as soon as new shrink-ed halt_poll_ns value falls below halt_poll_ns_grow_start. Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210902031100.252080-1-senozhatsky@chromium.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-06KVM: Drop unused kvm_dirty_gfn_invalid()Peter Xu1-5/+0
Drop the unused function as reported by test bot. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20210901230904.15164-1-peterx@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-06Merge tag 'kvmarm-5.15' of ↵Paolo Bonzini1-18/+1
git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD KVM/arm64 updates for 5.15 - Page ownership tracking between host EL1 and EL2 - Rely on userspace page tables to create large stage-2 mappings - Fix incompatibility between pKVM and kmemleak - Fix the PMU reset state, and improve the performance of the virtual PMU - Move over to the generic KVM entry code - Address PSCI reset issues w.r.t. save/restore - Preliminary rework for the upcoming pKVM fixed feature - A bunch of MM cleanups - a vGIC fix for timer spurious interrupts - Various cleanups
2021-09-06KVM: stats: Add VM stat for remote tlb flush requestsJing Zhang1-0/+1
Add a new stat that counts the number of times a remote TLB flush is requested, regardless of whether it kicks vCPUs out of guest mode. This allows us to look at how often flushes are initiated. Unlike remote_tlb_flush, this one applies to ARM's instruction-set-based TLB flush implementation, so apply it there too. Original-by: David Matlack <dmatlack@google.com> Signed-off-by: Jing Zhang <jingzhangos@google.com> Message-Id: <20210817002639.3856694-1-jingzhangos@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-06KVM: Remove unnecessary export of kvm_{inc,dec}_notifier_count()Sean Christopherson1-3/+0
Don't export KVM's MMU notifier count helpers, under no circumstance should any downstream module, including x86's vendor code, have a legitimate reason to piggyback KVM's MMU notifier logic. E.g in the x86 case, only KVM's MMU should be elevating the notifier count, and that code is always built into the core kvm.ko module. Fixes: edb298c663fc ("KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range") Cc: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210902175951.1387989-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-20KVM: stats: Add halt polling related histogram statsJing Zhang1-0/+12
Add three log histogram stats to record the distribution of time spent on successful polling, failed polling and VCPU wait. halt_poll_success_hist: Distribution of spent time for a successful poll. halt_poll_fail_hist: Distribution of spent time for a failed poll. halt_wait_hist: Distribution of time a VCPU has spent on waiting. Signed-off-by: Jing Zhang <jingzhangos@google.com> Message-Id: <20210802165633.1866976-6-jingzhangos@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-20KVM: stats: Add halt_wait_ns stats for all architecturesJing Zhang1-0/+4
Add simple stats halt_wait_ns to record the time a VCPU has spent on waiting for all architectures (not just powerpc). Signed-off-by: Jing Zhang <jingzhangos@google.com> Message-Id: <20210802165633.1866976-5-jingzhangos@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-20KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_rangeMaxim Levitsky1-2/+5
This together with previous patch, ensures that kvm_zap_gfn_range doesn't race with page fault running on another vcpu, and will make this page fault code retry instead. This is based on a patch suggested by Sean Christopherson: https://lkml.org/lkml/2021/7/22/1025 Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210810205251.424103-5-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-13KVM: Allow to have arch-specific per-vm debugfs filesPeter Xu1-1/+19
Allow archs to create arch-specific nodes under kvm->debugfs_dentry directory besides the stats fields. The new interface kvm_arch_create_vm_debugfs() is defined but not yet used. It's called after kvm->debugfs_dentry is created, so it can be referenced directly in kvm_arch_create_vm_debugfs(). Arch should define their own versions when they want to create extra debugfs nodes. Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20210730220455.26054-2-peterx@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-13KVM: stats: remove dead storesPaolo Bonzini1-2/+0
These stores are copied and pasted from the "if" statements above. They are dead and while they are not really a bug, they can be confusing to anyone reading the code as well. Remove them. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-10Merge branch 'kvm-vmx-secctl' into HEADPaolo Bonzini1-2/+16
Merge common topic branch for 5.14-rc6 and 5.15 merge window.
2021-08-06KVM: Cache the last used slot index per vCPUDavid Matlack1-1/+21
The memslot for a given gfn is looked up multiple times during page fault handling. Avoid binary searching for it multiple times by caching the most recently used slot. There is an existing VM-wide last_used_slot but that does not work well for cases where vCPUs are accessing memory in different slots (see performance data below). Another benefit of caching the most recently use slot (versus looking up the slot once and passing around a pointer) is speeding up memslot lookups *across* faults and during spte prefetching. To measure the performance of this change I ran dirty_log_perf_test with 64 vCPUs and 64 memslots and measured "Populate memory time" and "Iteration 2 dirty memory time". Tests were ran with eptad=N to force dirty logging to use fast_page_fault so its performance could be measured. Config | Metric | Before | After ---------- | ----------------------------- | ------ | ------ tdp_mmu=Y | Populate memory time | 6.76s | 5.47s tdp_mmu=Y | Iteration 2 dirty memory time | 2.83s | 0.31s tdp_mmu=N | Populate memory time | 20.4s | 18.7s tdp_mmu=N | Iteration 2 dirty memory time | 2.65s | 0.30s The "Iteration 2 dirty memory time" results are especially compelling because they are equivalent to running the same test with a single memslot. In other words, fast_page_fault performance no longer scales with the number of memslots. Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210804222844.1419481-4-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-06KVM: Rename lru_slot to last_used_slotDavid Matlack1-2/+2
lru_slot is used to keep track of the index of the most-recently used memslot. The correct acronym would be "mru" but that is not a common acronym. So call it last_used_slot which is a bit more obvious. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210804222844.1419481-2-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-04KVM: Do not leak memory for duplicate debugfs directoriesPaolo Bonzini1-2/+16
KVM creates a debugfs directory for each VM in order to store statistics about the virtual machine. The directory name is built from the process pid and a VM fd. While generally unique, it is possible to keep a file descriptor alive in a way that causes duplicate directories, which manifests as these messages: [ 471.846235] debugfs: Directory '20245-4' with parent 'kvm' already present! Even though this should not happen in practice, it is more or less expected in the case of KVM for testcases that call KVM_CREATE_VM and close the resulting file descriptor repeatedly and in parallel. When this happens, debugfs_create_dir() returns an error but kvm_create_vm_debugfs() goes on to allocate stat data structs which are later leaked. The slow memory leak was spotted by syzkaller, where it caused OOM reports. Since the issue only affects debugfs, do a lookup before calling debugfs_create_dir, so that the message is downgraded and rate-limited. While at it, ensure kvm->debugfs_dentry is NULL rather than an error if it is not created. This fixes kvm_destroy_vm_debugfs, which was not checking IS_ERR_OR_NULL correctly. Cc: stable@vger.kernel.org Fixes: 536a6f88c49d ("KVM: Create debugfs dir and stat files for each VM") Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-03KVM: Don't take mmu_lock for range invalidation unless necessaryPaolo Bonzini1-13/+12
Avoid taking mmu_lock for .invalidate_range_{start,end}() notifications that are unrelated to KVM. This is possible now that memslot updates are blocked from range_start() to range_end(); that ensures that lock elision happens in both or none, and therefore that mmu_notifier_count updates (which must occur while holding mmu_lock for write) are always paired across start->end. Based on patches originally written by Ben Gardon. Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-03KVM: Block memslot updates across range_start() and range_end()Paolo Bonzini1-4/+54
We would like to avoid taking mmu_lock for .invalidate_range_{start,end}() notifications that are unrelated to KVM. Because mmu_notifier_count must be modified while holding mmu_lock for write, and must always be paired across start->end to stay balanced, lock elision must happen in both or none. Therefore, in preparation for this change, this patch prevents memslot updates across range_start() and range_end(). Note, technically flag-only memslot updates could be allowed in parallel, but stalling a memslot update for a relatively short amount of time is not a scalability issue, and this is all more than complex enough. A long note on the locking: a previous version of the patch used an rwsem to block the memslot update while the MMU notifier run, but this resulted in the following deadlock involving the pseudo-lock tagged as "mmu_notifier_invalidate_range_start". ====================================================== WARNING: possible circular locking dependency detected 5.12.0-rc3+ #6 Tainted: G OE ------------------------------------------------------ qemu-system-x86/3069 is trying to acquire lock: ffffffff9c775ca0 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: __mmu_notifier_invalidate_range_end+0x5/0x190 but task is already holding lock: ffffaff7410a9160 (&kvm->mmu_notifier_slots_lock){.+.+}-{3:3}, at: kvm_mmu_notifier_invalidate_range_start+0x36d/0x4f0 [kvm] which lock already depends on the new lock. This corresponds to the following MMU notifier logic: invalidate_range_start take pseudo lock down_read() (*) release pseudo lock invalidate_range_end take pseudo lock (**) up_read() release pseudo lock At point (*) we take the mmu_notifiers_slots_lock inside the pseudo lock; at point (**) we take the pseudo lock inside the mmu_notifiers_slots_lock. This could cause a deadlock (ignoring for a second that the pseudo lock is not a lock): - invalidate_range_start waits on down_read(), because the rwsem is held by install_new_memslots - install_new_memslots waits on down_write(), because the rwsem is held till (another) invalidate_range_end finishes - invalidate_range_end sits waits on the pseudo lock, held by invalidate_range_start. Removing the fairness of the rwsem breaks the cycle (in lockdep terms, it would change the *shared* rwsem readers into *shared recursive* readers), so open-code the wait using a readers count and a spinlock. This also allows handling blockable and non-blockable critical section in the same way. Losing the rwsem fairness does theoretically allow MMU notifiers to block install_new_memslots forever. Note that mm/mmu_notifier.c's own retry scheme in mmu_interval_read_begin also uses wait/wake_up and is likewise not fair. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-02KVM: Introduce kvm_get_kvm_safe()Peter Xu1-5/+15
Introduce this safe version of kvm_get_kvm() so that it can be called even during vm destruction. Use it in kvm_debugfs_open() and remove the verbose comment. Prepare to be used elsewhere. Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20210625153214.43106-3-peterx@redhat.com> [Preserve the comment in kvm_debugfs_open. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-02KVM: Add infrastructure and macro to mark VM as buggedSean Christopherson1-5/+5
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <3a0998645c328bf0895f1290e61821b70f048549.1625186503.git.isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-08-02KVM: Get rid of kvm_get_pfn()Marc Zyngier1-8/+1
Nobody is using kvm_get_pfn() anymore. Get rid of it. Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20210726153552.1535838-7-maz@kernel.org
2021-08-02KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap()Marc Zyngier1-10/+0
Now that arm64 has stopped using kvm_is_transparent_hugepage(), we can remove it, as well as PageTransCompoundMap() which was only used by the former. Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20210726153552.1535838-5-maz@kernel.org
2021-07-27KVM: add missing compat KVM_CLEAR_DIRTY_LOGPaolo Bonzini1-0/+28
The arguments to the KVM_CLEAR_DIRTY_LOG ioctl include a pointer, therefore it needs a compat ioctl implementation. Otherwise, 32-bit userspace fails to invoke it on 64-bit kernels; for x86 it might work fine by chance if the padding is zero, but not on big-endian architectures. Reported-by: Thomas Sattler Cc: stable@vger.kernel.org Fixes: 2a31b9db1535 ("kvm: introduce manual dirty log reprotect") Reviewed-by: Peter Xu <peterx@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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