kernel/linux.git/drivers/xen, branch v6.6

xen/events: replace evtchn_rwlock with RCU

2023-10-09T07:21:16+00:00

In unprivileged Xen guests event handling can cause a deadlock with Xen console handling. The evtchn_rwlock and the hvc_lock are taken in opposite sequence in __hvc_poll() and in Xen console IRQ handling. Normally this is no problem, as the evtchn_rwlock is taken as a reader in both paths, but as soon as an event channel is being closed, the lock will be taken as a writer, which will cause read_lock() to block: CPU0 CPU1 CPU2 (IRQ handling) (__hvc_poll()) (closing event channel) read_lock(evtchn_rwlock) spin_lock(hvc_lock) write_lock(evtchn_rwlock) [blocks] spin_lock(hvc_lock) [blocks] read_lock(evtchn_rwlock) [blocks due to writer waiting, and not in_interrupt()] This issue can be avoided by replacing evtchn_rwlock with RCU in xen_free_irq(). Note that RCU is used only to delay freeing of the irq_info memory. There is no RCU based dereferencing or replacement of pointers involved. In order to avoid potential races between removing the irq_info reference and handling of interrupts, set the irq_info pointer to NULL only when freeing its memory. The IRQ itself must be freed at that time, too, as otherwise the same IRQ number could be allocated again before handling of the old instance would have been finished. This is XSA-441 / CVE-2023-34324. Fixes: 54c9de89895e ("xen/events: add a new "late EOI" evtchn framework") Reported-by: Marek Marczykowski-Górecki Signed-off-by: Juergen Gross Reviewed-by: Julien Grall Signed-off-by: Juergen Gross

xen: simplify evtchn_do_upcall() call maze

2023-09-19T05:04:49+00:00

There are several functions involved for performing the functionality of evtchn_do_upcall(): - __xen_evtchn_do_upcall() doing the real work - xen_hvm_evtchn_do_upcall() just being a wrapper for __xen_evtchn_do_upcall(), exposed for external callers - xen_evtchn_do_upcall() calling __xen_evtchn_do_upcall(), too, but without any user Simplify this maze by: - removing the unused xen_evtchn_do_upcall() - removing xen_hvm_evtchn_do_upcall() as the only left caller of __xen_evtchn_do_upcall(), while renaming __xen_evtchn_do_upcall() to xen_evtchn_do_upcall() Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Reviewed-by: Thomas Gleixner Signed-off-by: Juergen Gross

Merge tag 'dma-mapping-6.6-2023-08-29' of git://git.infradead.org/users/hch/dma-mapping

2023-08-30T03:32:10+00:00

Pull dma-maping updates from Christoph Hellwig: - allow dynamic sizing of the swiotlb buffer, to cater for secure virtualization workloads that require all I/O to be bounce buffered (Petr Tesarik) - move a declaration to a header (Arnd Bergmann) - check for memory region overlap in dma-contiguous (Binglei Wang) - remove the somewhat dangerous runtime swiotlb-xen enablement and unexport is_swiotlb_active (Christoph Hellwig, Juergen Gross) - per-node CMA improvements (Yajun Deng) * tag 'dma-mapping-6.6-2023-08-29' of git://git.infradead.org/users/hch/dma-mapping: swiotlb: optimize get_max_slots() swiotlb: move slot allocation explanation comment where it belongs swiotlb: search the software IO TLB only if the device makes use of it swiotlb: allocate a new memory pool when existing pools are full swiotlb: determine potential physical address limit swiotlb: if swiotlb is full, fall back to a transient memory pool swiotlb: add a flag whether SWIOTLB is allowed to grow swiotlb: separate memory pool data from other allocator data swiotlb: add documentation and rename swiotlb_do_find_slots() swiotlb: make io_tlb_default_mem local to swiotlb.c swiotlb: bail out of swiotlb_init_late() if swiotlb is already allocated dma-contiguous: check for memory region overlap dma-contiguous: support numa CMA for specified node dma-contiguous: support per-numa CMA for all architectures dma-mapping: move arch_dma_set_mask() declaration to header swiotlb: unexport is_swiotlb_active x86: always initialize xen-swiotlb when xen-pcifront is enabling xen/pci: add flag for PCI passthrough being possible

xen: privcmd: Add support for irqfd

2023-08-22T10:12:50+00:00

Xen provides support for injecting interrupts to the guests via the HYPERVISOR_dm_op() hypercall. The same is used by the Virtio based device backend implementations, in an inefficient manner currently. Generally, the Virtio backends are implemented to work with the Eventfd based mechanism. In order to make such backends work with Xen, another software layer needs to poll the Eventfds and raise an interrupt to the guest using the Xen based mechanism. This results in an extra context switch. This is not a new problem in Linux though. It is present with other hypervisors like KVM, etc. as well. The generic solution implemented in the kernel for them is to provide an IOCTL call to pass the interrupt details and eventfd, which lets the kernel take care of polling the eventfd and raising of the interrupt, instead of handling this in user space (which involves an extra context switch). This patch adds support to inject a specific interrupt to guest using the eventfd mechanism, by preventing the extra context switch. Inspired by existing implementations for KVM, etc.. Signed-off-by: Viresh Kumar Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/8e724ac1f50c2bc1eb8da9b3ff6166f1372570aa.1692697321.git.viresh.kumar@linaro.org Signed-off-by: Juergen Gross

xen/xenbus: Avoid a lockdep warning when adding a watch

2023-08-22T06:04:59+00:00

The following lockdep warning appears during boot on a Xen dom0 system: [ 96.388794] ====================================================== [ 96.388797] WARNING: possible circular locking dependency detected [ 96.388799] 6.4.0-rc5-default+ #8 Tainted: G EL [ 96.388803] ------------------------------------------------------ [ 96.388804] xenconsoled/1330 is trying to acquire lock: [ 96.388808] ffffffff82acdd10 (xs_watch_rwsem){++++}-{3:3}, at: register_xenbus_watch+0x45/0x140 [ 96.388847] but task is already holding lock: [ 96.388849] ffff888100c92068 (&u->msgbuffer_mutex){+.+.}-{3:3}, at: xenbus_file_write+0x2c/0x600 [ 96.388862] which lock already depends on the new lock. [ 96.388864] the existing dependency chain (in reverse order) is: [ 96.388866] -> #2 (&u->msgbuffer_mutex){+.+.}-{3:3}: [ 96.388874] __mutex_lock+0x85/0xb30 [ 96.388885] xenbus_dev_queue_reply+0x48/0x2b0 [ 96.388890] xenbus_thread+0x1d7/0x950 [ 96.388897] kthread+0xe7/0x120 [ 96.388905] ret_from_fork+0x2c/0x50 [ 96.388914] -> #1 (xs_response_mutex){+.+.}-{3:3}: [ 96.388923] __mutex_lock+0x85/0xb30 [ 96.388930] xenbus_backend_ioctl+0x56/0x1c0 [ 96.388935] __x64_sys_ioctl+0x90/0xd0 [ 96.388942] do_syscall_64+0x5c/0x90 [ 96.388950] entry_SYSCALL_64_after_hwframe+0x72/0xdc [ 96.388957] -> #0 (xs_watch_rwsem){++++}-{3:3}: [ 96.388965] __lock_acquire+0x1538/0x2260 [ 96.388972] lock_acquire+0xc6/0x2b0 [ 96.388976] down_read+0x2d/0x160 [ 96.388983] register_xenbus_watch+0x45/0x140 [ 96.388990] xenbus_file_write+0x53d/0x600 [ 96.388994] vfs_write+0xe4/0x490 [ 96.389003] ksys_write+0xb8/0xf0 [ 96.389011] do_syscall_64+0x5c/0x90 [ 96.389017] entry_SYSCALL_64_after_hwframe+0x72/0xdc [ 96.389023] other info that might help us debug this: [ 96.389025] Chain exists of: xs_watch_rwsem --> xs_response_mutex --> &u->msgbuffer_mutex [ 96.413429] Possible unsafe locking scenario: [ 96.413430] CPU0 CPU1 [ 96.413430] ---- ---- [ 96.413431] lock(&u->msgbuffer_mutex); [ 96.413432] lock(xs_response_mutex); [ 96.413433] lock(&u->msgbuffer_mutex); [ 96.413434] rlock(xs_watch_rwsem); [ 96.413436] *** DEADLOCK *** [ 96.413436] 1 lock held by xenconsoled/1330: [ 96.413438] #0: ffff888100c92068 (&u->msgbuffer_mutex){+.+.}-{3:3}, at: xenbus_file_write+0x2c/0x600 [ 96.413446] An ioctl call IOCTL_XENBUS_BACKEND_SETUP (record #1 in the report) results in calling xenbus_alloc() -> xs_suspend() which introduces ordering xs_watch_rwsem --> xs_response_mutex. The xenbus_thread() operation (record #2) creates xs_response_mutex --> &u->msgbuffer_mutex. An XS_WATCH write to the xenbus file then results in a complain about the opposite lock order &u->msgbuffer_mutex --> xs_watch_rwsem. The dependency xs_watch_rwsem --> xs_response_mutex is spurious. Avoid it and the warning by changing the ordering in xs_suspend(), first acquire xs_response_mutex and then xs_watch_rwsem. Reverse also the unlocking order in xs_suspend_cancel() for consistency, but keep xs_resume() as is because it needs to have xs_watch_rwsem unlocked only after exiting xs suspend and re-adding all watches. Signed-off-by: Petr Pavlu Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20230607123624.15739-1-petr.pavlu@suse.com Signed-off-by: Juergen Gross

xen: Fix one kernel-doc comment

2023-08-21T13:58:57+00:00

Use colon to separate parameter name from their specific meaning. silence the warning: drivers/xen/grant-table.c:1051: warning: Function parameter or member 'nr_pages' not described in 'gnttab_free_pages' Reported-by: Abaci Robot Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=6030 Signed-off-by: Yang Li Acked-by: Juergen Gross Link: https://lore.kernel.org/r/20230731030037.123946-1-yang.lee@linux.alibaba.com Signed-off-by: Juergen Gross

xen: xenbus: Use helper function IS_ERR_OR_NULL()

2023-08-21T07:55:11+00:00

Use IS_ERR_OR_NULL() to detect an error pointer or a null pointer open-coding to simplify the code. Signed-off-by: Li Zetao Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20230817014736.3094289-1-lizetao1@huawei.com Signed-off-by: Juergen Gross

xen: Switch to use kmemdup() helper

2023-08-21T07:54:05+00:00

Use kmemdup() helper instead of open-coding to simplify the code. Signed-off-by: Ruan Jinjie Reviewed-by: Juergen Gross Reviewed-by: Chen Jiahao Link: https://lore.kernel.org/r/20230815092434.1206386-1-ruanjinjie@huawei.com Signed-off-by: Juergen Gross

xen-pciback: Remove unused function declarations

2023-08-21T07:53:22+00:00

Commit a92336a1176b ("xen/pciback: Drop two backends, squash and cleanup some code.") declared but never implemented these functions. Signed-off-by: Yue Haibing Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20230808150912.43416-1-yuehaibing@huawei.com Signed-off-by: Juergen Gross

swiotlb: make io_tlb_default_mem local to swiotlb.c

2023-08-01T16:02:09+00:00

SWIOTLB implementation details should not be exposed to the rest of the kernel. This will allow to make changes to the implementation without modifying non-swiotlb code. To avoid breaking existing users, provide helper functions for the few required fields. As a bonus, using a helper function to initialize struct device allows to get rid of an #ifdef in driver core. Signed-off-by: Petr Tesarik Reviewed-by: Greg Kroah-Hartman Signed-off-by: Christoph Hellwig