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2020-06-01Revert "KVM: No need to retry for hva_to_pfn_remapped()"Paolo Bonzini1-0/+5
This reverts commit 5b494aea13fe9ec67365510c0d75835428cbb303. If unlocked==true then the vma pointer could be invalidated, so the 2nd follow_pfn() is potentially racy: we do need to get out and redo find_vma_intersection(). Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATEPaolo Bonzini6-7/+171
Similar to VMX, the state that is captured through the currently available IOCTLs is a mix of L1 and L2 state, dependent on whether the L2 guest was running at the moment when the process was interrupted to save its state. In particular, the SVM-specific state for nested virtualization includes the L1 saved state (including the interrupt flag), the cached L2 controls, and the GIF. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01selftests: kvm: fix smm test on SVMVitaly Kuznetsov1-6/+13
KVM_CAP_NESTED_STATE is now supported for AMD too but smm test acts like it is still Intel only. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20200529130407.57176-2-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01selftests: kvm: add a SVM version of state-testPaolo Bonzini1-12/+50
The test is similar to the existing one for VMX, but simpler because we don't have to test shadow VMCS or vmptrld/vmptrst/vmclear. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01selftests: kvm: introduce cpu_has_svm() checkVitaly Kuznetsov1-0/+10
Many tests will want to check if the CPU is Intel or AMD in guest code, add cpu_has_svm() and put it as static inline to svm_util.h. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20200529130407.57176-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: MMU: pass arbitrary CR0/CR4/EFER to kvm_init_shadow_mmuPaolo Bonzini3-7/+14
This allows fetching the registers from the hsave area when setting up the NPT shadow MMU, and is needed for KVM_SET_NESTED_STATE (which runs long after the CR0, CR4 and EFER values in vcpu have been switched to hold L2 guest state). Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: leave guest mode when clearing EFER.SVMEPaolo Bonzini3-2/+25
According to the AMD manual, the effect of turning off EFER.SVME while a guest is running is undefined. We make it leave guest mode immediately, similar to the effect of clearing the VMX bit in MSR_IA32_FEAT_CTL. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: split nested_vmcb_check_controlsPaolo Bonzini1-9/+14
The authoritative state does not come from the VMCB once in guest mode, but KVM_SET_NESTED_STATE can still perform checks on L1's provided SVM controls because we get them from userspace. Therefore, split out a function to do them. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: remove HF_HIF_MASKPaolo Bonzini3-7/+1
The L1 flags can be found in the save area of svm->nested.hsave, fish it from there so that there is one fewer thing to migrate. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: remove HF_VINTR_MASKPaolo Bonzini4-8/+5
Now that the int_ctl field is stored in svm->nested.ctl.int_ctl, we can use it instead of vcpu->arch.hflags to check whether L2 is running in V_INTR_MASKING mode. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: synthesize correct EXITINTINFO on vmexitPaolo Bonzini2-14/+49
This bit was added to nested VMX right when nested_run_pending was introduced, but it is not yet there in nSVM. Since we can have pending events that L0 injected directly into L2 on vmentry, we have to transfer them into L1's queue. For this to work, one important change is required: svm_complete_interrupts (which clears the "injected" fields from the previous VMRUN, and updates them from svm->vmcb's EXITINTINFO) must be placed before we inject the vmexit. This is not too scary though; VMX even does it in vmx_vcpu_run. While at it, the nested_vmexit_inject tracepoint is moved towards the end of nested_svm_vmexit. This ensures that the synthesized EXITINTINFO is visible in the trace. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: SVM: preserve VGIF across VMCB switchPaolo Bonzini1-1/+5
There is only one GIF flag for the whole processor, so make sure it is not clobbered when switching to L2 (in which case we also have to include the V_GIF_ENABLE_MASK, lest we confuse enable_gif/disable_gif/gif_set). When going back, L1 could in theory have entered L2 without issuing a CLGI so make sure the svm_set_gif is done last, after svm->vmcb->control.int_ctl has been copied back from hsave. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: extract svm_set_gifPaolo Bonzini4-37/+38
Extract the code that is needed to implement CLGI and STGI, so that we can run it from VMRUN and vmexit (and in the future, KVM_SET_NESTED_STATE). Skip the request for KVM_REQ_EVENT unless needed, subsuming the evaluate_pending_interrupts optimization that is found in enter_svm_guest_mode. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: remove unnecessary ifPaolo Bonzini1-2/+1
kvm_vcpu_apicv_active must be false when nested virtualization is enabled, so there is no need to check it in clgi_interception. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: synchronize VMCB controls updated by the processor on every vmexitPaolo Bonzini3-25/+38
The control state changes on every L2->L0 vmexit, and we will have to serialize it in the nested state. So keep it up to date in svm->nested.ctl and just copy them back to the nested VMCB in nested_svm_vmexit. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: restore clobbered INT_CTL fields after clearing VINTRPaolo Bonzini1-1/+9
Restore the INT_CTL value from the guest's VMCB once we've stopped using it, so that virtual interrupts can be injected as requested by L1. V_TPR is up-to-date however, and it can change if the guest writes to CR8, so keep it. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: save all control fields in svm->nestedPaolo Bonzini3-58/+39
In preparation for nested SVM save/restore, store all data that matters from the VMCB control area into svm->nested. It will then become part of the nested SVM state that is saved by KVM_SET_NESTED_STATE and restored by KVM_GET_NESTED_STATE, just like the cached vmcs12 for nVMX. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: remove trailing padding for struct vmcb_control_areaPaolo Bonzini1-1/+8
Allow placing the VMCB structs on the stack or in other structs without wasting too much space. Add BUILD_BUG_ON as a quick safeguard against typos. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: pass vmcb_control_area to copy_vmcb_control_areaPaolo Bonzini1-6/+4
This will come in handy when we put a struct vmcb_control_area in svm->nested. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: clean up tsc_offset updatePaolo Bonzini1-4/+5
Use l1_tsc_offset to compute svm->vcpu.arch.tsc_offset and svm->vmcb->control.tsc_offset, instead of relying on hsave. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: move MMU setup to nested_prepare_vmcb_controlPaolo Bonzini1-6/+6
Everything that is needed during nested state restore is now part of nested_prepare_vmcb_control. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: extract preparation of VMCB for nested runPaolo Bonzini1-16/+24
Split out filling svm->vmcb.save and svm->vmcb.control before VMRUN. Only the latter will be useful when restoring nested SVM state. This patch introduces no semantic change, so the MMU setup is still done in nested_prepare_vmcb_save. The next patch will clean up things. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: extract load_nested_vmcb_controlPaolo Bonzini1-16/+22
When restoring SVM nested state, the control state cache in svm->nested will have to be filled, but the save state will not have to be moved into svm->vmcb. Therefore, pull the code that handles the control area into a separate function. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-01KVM: nSVM: move map argument out of enter_svm_guest_modePaolo Bonzini3-10/+9
Unmapping the nested VMCB in enter_svm_guest_mode is a bit of a wart, since the map argument is not used elsewhere in the function. There are just two callers, and those are also the place where kvm_vcpu_map is called, so it is cleaner to unmap there. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-28KVM: nVMX: always update CR3 in VMCSPaolo Bonzini1-4/+1
vmx_load_mmu_pgd is delaying the write of GUEST_CR3 to prepare_vmcs02 as an optimization, but this is only correct before the nested vmentry. If userspace is modifying CR3 with KVM_SET_SREGS after the VM has already been put in guest mode, the value of CR3 will not be updated. Remove the optimization, which almost never triggers anyway. Fixes: 04f11ef45810 ("KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter") Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-28KVM: SVM: always update CR3 in VMCBPaolo Bonzini2-16/+6
svm_load_mmu_pgd is delaying the write of GUEST_CR3 to prepare_vmcs02 as an optimization, but this is only correct before the nested vmentry. If userspace is modifying CR3 with KVM_SET_SREGS after the VM has already been put in guest mode, the value of CR3 will not be updated. Remove the optimization, which almost never triggers anyway. This was was added in commit 689f3bf21628 ("KVM: x86: unify callbacks to load paging root", 2020-03-16) just to keep the two vendor-specific modules closer, but we'll fix VMX too. Fixes: 689f3bf21628 ("KVM: x86: unify callbacks to load paging root") Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-28KVM: nSVM: correctly inject INIT vmexitsPaolo Bonzini1-0/+27
The usual drill at this point, except there is no code to remove because this case was not handled at all. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-28KVM: nSVM: remove exit_requiredPaolo Bonzini3-19/+1
All events now inject vmexits before vmentry rather than after vmexit. Therefore, exit_required is not set anymore and we can remove it. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-28KVM: nSVM: inject exceptions via svm_check_nested_eventsPaolo Bonzini5-103/+58
This allows exceptions injected by the emulator to be properly delivered as vmexits. The code also becomes simpler, because we can just let all L0-intercepted exceptions go through the usual path. In particular, our emulation of the VMX #DB exit qualification is very much simplified, because the vmexit injection path can use kvm_deliver_exception_payload to update DR6. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-28KVM: x86: enable event window in inject_pending_eventPaolo Bonzini4-77/+92
In case an interrupt arrives after nested.check_events but before the call to kvm_cpu_has_injectable_intr, we could end up enabling the interrupt window even if the interrupt is actually going to be a vmexit. This is useless rather than harmful, but it really complicates reasoning about SVM's handling of the VINTR intercept. We'd like to never bother with the VINTR intercept if V_INTR_MASKING=1 && INTERCEPT_INTR=1, because in that case there is no interrupt window and we can just exit the nested guest whenever we want. This patch moves the opening of the interrupt window inside inject_pending_event. This consolidates the check for pending interrupt/NMI/SMI in one place, and makes KVM's usage of immediate exits more consistent, extending it beyond just nested virtualization. There are two functional changes here. They only affect corner cases, but overall they simplify the inject_pending_event. - re-injection of still-pending events will also use req_immediate_exit instead of using interrupt-window intercepts. This should have no impact on performance on Intel since it simply replaces an interrupt-window or NMI-window exit for a preemption-timer exit. On AMD, which has no equivalent of the preemption time, it may incur some overhead but an actual effect on performance should only be visible in pathological cases. - kvm_arch_interrupt_allowed and kvm_vcpu_has_events will return true if an interrupt, NMI or SMI is blocked by nested_run_pending. This makes sense because entering the VM will allow it to make progress and deliver the event. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86: track manually whether an event has been injectedPaolo Bonzini1-5/+12
Instead of calling kvm_event_needs_reinjection, track its future return value in a variable. This will be useful in the next patch. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: nSVM: Preserve registers modifications done before nested_svm_vmexit()Vitaly Kuznetsov1-3/+3
L2 guest hang is observed after 'exit_required' was dropped and nSVM switched to check_nested_events() completely. The hang is a busy loop when e.g. KVM is emulating an instruction (e.g. L2 is accessing MMIO space and we drop to userspace). After nested_svm_vmexit() and when L1 is doing VMRUN nested guest's RIP is not advanced so KVM goes into emulating the same instruction which caused nested_svm_vmexit() and the loop continues. nested_svm_vmexit() is not new, however, with check_nested_events() we're now calling it later than before. In case by that time KVM has modified register state we may pick stale values from VMCB when trying to save nested guest state to nested VMCB. nVMX code handles this case correctly: sync_vmcs02_to_vmcs12() called from nested_vmx_vmexit() does e.g 'vmcs12->guest_rip = kvm_rip_read(vcpu)' and this ensures KVM-made modifications are preserved. Do the same for nSVM. Generally, nested_vmx_vmexit()/nested_svm_vmexit() need to pick up all nested guest state modifications done by KVM after vmexit. It would be great to find a way to express this in a way which would not require to manually track these changes, e.g. nested_{vmcb,vmcs}_get_field(). Co-debugged-with: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20200527090102.220647-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86: Initialize tdp_level during vCPU creationSean Christopherson1-0/+1
Initialize vcpu->arch.tdp_level during vCPU creation to avoid consuming garbage if userspace calls KVM_RUN without first calling KVM_SET_CPUID. Fixes: e93fd3b3e89e9 ("KVM: x86/mmu: Capture TDP level when updating CPUID") Reported-by: syzbot+904752567107eefb728c@syzkaller.appspotmail.com Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200527085400.23759-1-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: nSVM: leave ASID aside in copy_vmcb_control_areaPaolo Bonzini1-1/+1
Restoring the ASID from the hsave area on VMEXIT is wrong, because its value depends on the handling of TLB flushes. Just skipping the field in copy_vmcb_control_area will do. Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: nSVM: fix condition for filtering async PFPaolo Bonzini1-2/+2
Async page faults have to be trapped in the host (L1 in this case), since the APF reason was passed from L0 to L1 and stored in the L1 APF data page. This was completely reversed: the page faults were passed to the guest, a L2 hypervisor. Cc: stable@vger.kernel.org Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27kvm/x86: Remove redundant function implementations彭浩(Richard)5-16/+10
pic_in_kernel(), ioapic_in_kernel() and irqchip_kernel() have the same implementation. Signed-off-by: Peng Hao <richard.peng@oppo.com> Message-Id: <HKAPR02MB4291D5926EA10B8BFE9EA0D3E0B70@HKAPR02MB4291.apcprd02.prod.outlook.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: Fix the indentation to match coding styleHaiwei Li1-1/+1
There is a bad indentation in next&queue branch. The patch looks like fixes nothing though it fixes the indentation. Before fixing: if (!handle_fastpath_set_x2apic_icr_irqoff(vcpu, data)) { kvm_skip_emulated_instruction(vcpu); ret = EXIT_FASTPATH_EXIT_HANDLED; } break; case MSR_IA32_TSCDEADLINE: After fixing: if (!handle_fastpath_set_x2apic_icr_irqoff(vcpu, data)) { kvm_skip_emulated_instruction(vcpu); ret = EXIT_FASTPATH_EXIT_HANDLED; } break; case MSR_IA32_TSCDEADLINE: Signed-off-by: Haiwei Li <lihaiwei@tencent.com> Message-Id: <2f78457e-f3a7-3bc9-e237-3132ee87f71e@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: VMX: replace "fall through" with "return" to indicate different caseMiaohe Lin1-4/+2
The second "/* fall through */" in rmode_exception() makes code harder to read. Replace it with "return" to indicate they are different cases, only the #DB and #BP check vcpu->guest_debug, while others don't care. And this also improves the readability. Suggested-by: Vitaly Kuznetsov <vkuznets@redhat.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Message-Id: <1582080348-20827-1-git-send-email-linmiaohe@huawei.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86: Take an unsigned 32-bit int for has_emulated_msr()'s indexSean Christopherson3-3/+3
Take a u32 for the index in has_emulated_msr() to match hardware, which treats MSR indices as unsigned 32-bit values. Functionally, taking a signed int doesn't cause problems with the current code base, but could theoretically cause problems with 32-bit KVM, e.g. if the index were checked via a less-than statement, which would evaluate incorrectly for MSR indices with bit 31 set. Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200218234012.7110-3-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86: Remove superfluous brackets from case statementSean Christopherson1-2/+2
Remove unnecessary brackets from a case statement that unintentionally encapsulates unrelated case statements in the same switch statement. While technically legal and functionally correct syntax, the brackets are visually confusing and potentially dangerous, e.g. the last of the encapsulated case statements has an undocumented fall-through that isn't flagged by compilers due the encapsulation. Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200218234012.7110-2-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86: allow KVM_STATE_NESTED_MTF_PENDING in kvm_state flagsPaolo Bonzini1-1/+1
The migration functionality was left incomplete in commit 5ef8acbdd687 ("KVM: nVMX: Emulate MTF when performing instruction emulation", 2020-02-23), fix it. Fixes: 5ef8acbdd687 ("KVM: nVMX: Emulate MTF when performing instruction emulation") Cc: stable@vger.kernel.org Reviewed-by: Oliver Upton <oupton@google.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27Merge branch 'kvm-master' into HEADPaolo Bonzini5-39/+33
Merge AMD fixes before doing more development work.
2020-05-27Merge tag 'kvm-s390-next-5.8-1' of ↵Paolo Bonzini3-8/+7
git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD KVM: s390: Cleanups for 5.8 - vsie (nesting) cleanups - remove unneeded semicolon
2020-05-27KVM: x86: simplify is_mmio_sptePaolo Bonzini4-11/+6
We can simply look at bits 52-53 to identify MMIO entries in KVM's page tables. Therefore, there is no need to pass a mask to kvm_mmu_set_mmio_spte_mask. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionallyMaxim Levitsky1-0/+4
This msr is only available when the host supports WAITPKG feature. This breaks a nested guest, if the L1 hypervisor is set to ignore unknown msrs, because the only other safety check that the kernel does is that it attempts to read the msr and rejects it if it gets an exception. Cc: stable@vger.kernel.org Fixes: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL") Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: VMX: enable X86_FEATURE_WAITPKG in KVM capabilitiesMaxim Levitsky1-0/+3
Even though we might not allow the guest to use WAITPKG's new instructions, we should tell KVM that the feature is supported by the host CPU. Note that vmx_waitpkg_supported checks that WAITPKG _can_ be set in secondary execution controls as specified by VMX capability MSR, rather that we actually enable it for a guest. Cc: stable@vger.kernel.org Fixes: e69e72faa3a0 ("KVM: x86: Add support for user wait instructions") Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20200523161455.3940-2-mlevitsk@redhat.com> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-27KVM: x86/mmu: Set mmio_value to '0' if reserved #PF can't be generatedSean Christopherson1-18/+9
Set the mmio_value to '0' instead of simply clearing the present bit to squash a benign warning in kvm_mmu_set_mmio_spte_mask() that complains about the mmio_value overlapping the lower GFN mask on systems with 52 bits of PA space. Opportunistically clean up the code and comments. Cc: stable@vger.kernel.org Fixes: d43e2675e96fc ("KVM: x86: only do L1TF workaround on affected processors") Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200527084909.23492-1-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-20Merge tag 'noinstr-x86-kvm-2020-05-16' of ↵Paolo Bonzini868-4517/+8779
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into HEAD
2020-05-20rcuwait: avoid lockdep splats from rcuwait_active()Paolo Bonzini1-1/+1
rcuwait_active only returns whether w->task is not NULL. This is exactly one of the usecases that are mentioned in the documentation for rcu_access_pointer() where it is correct to bypass lockdep checks. This avoids a splat from kvm_vcpu_on_spin(). Reported-by: Wanpeng Li <kernellwp@gmail.com> Tested-by: Wanpeng Li <kernellwp@gmail.com> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-05-19x86/kvm: Restrict ASYNC_PF to user spaceThomas Gleixner1-93/+7
The async page fault injection into kernel space creates more problems than it solves. The host has absolutely no knowledge about the state of the guest if the fault happens in CPL0. The only restriction for the host is interrupt disabled state. If interrupts are enabled in the guest then the exception can hit arbitrary code. The HALT based wait in non-preemotible code is a hacky replacement for a proper hypercall. For the ongoing work to restrict instrumentation and make the RCU idle interaction well defined the required extra work for supporting async pagefault in CPL0 is just not justified and creates complexity for a dubious benefit. The CPL3 injection is well defined and does not cause any issues as it is more or less the same as a regular page fault from CPL3. Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134059.369802541@linutronix.de
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