- Jul 11, 2024
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commit 49f683b4 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: 217ece61 ("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:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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- Apr 11, 2024
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[ Upstream commit 3d75b8aa ] 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 5f6de5cb ("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: af585b92 ("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:
Sasha Levin <sashal@kernel.org>
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- Oct 12, 2023
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[ Upstream commit 9e0f4f29 ] kvm_vfio_group_add() creates kvg instance, links it to kv->group_list, and calls kvm_vfio_file_set_kvm() with kvg->file as an argument after dropping kv->lock. If we race group addition and deletion calls, kvg instance may get freed by the time we get around to calling kvm_vfio_file_set_kvm(). Previous iterations of the code did not reference kvg->file outside of the critical section, but used a temporary variable. Still, they had similar problem of the file reference being owned by kvg structure and potential for kvm_vfio_group_del() dropping it before kvm_vfio_group_add() had a chance to complete. Fix this by moving call to kvm_vfio_file_set_kvm() under the protection of kv->lock. We already call it while holding the same lock when vfio group is being deleted, so it should be safe here as well. Fixes: 2fc1bec1 ("kvm: set/clear kvm to/from vfio_group when group add/delete") Reviewed-by:
Alex Williamson <alex.williamson@redhat.com> Signed-off-by:
Dmitry Torokhov <dmitry.torokhov@gmail.com> Reviewed-by:
Kevin Tian <kevin.tian@intel.com> Link: https://lore.kernel.org/r/20230714224538.404793-1-dmitry.torokhov@gmail.com Signed-off-by:
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[ Upstream commit 2f99073a ] This renames kvm_vfio_group related helpers to prepare for accepting vfio device fd. No functional change is intended. Reviewed-by:
Eric Auger <eric.auger@redhat.com> Reviewed-by:
Jason Gunthorpe <jgg@nvidia.com> Tested-by:
Terrence Xu <terrence.xu@intel.com> Tested-by:
Nicolin Chen <nicolinc@nvidia.com> Tested-by:
Matthew Rosato <mjrosato@linux.ibm.com> Tested-by:
Yanting Jiang <yanting.jiang@intel.com> Tested-by:
Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> Tested-by:
Zhenzhong Duan <zhenzhong.duan@intel.com> Signed-off-by:
Yi Liu <yi.l.liu@intel.com> Link: https://lore.kernel.org/r/20230718135551.6592-5-yi.l.liu@intel.com Signed-off-by:
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- Aug 17, 2023
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commit eed3013f 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: ce55c049 ("KVM: stats: Support binary stats retrieval for a VCPU") Fixes: fcfe1bae ("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:
Kees Cook <keescook@chromium.org> Message-Id: <20230711230131.648752-2-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com> Signed-off-by:
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commit 2230f9e1 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 cd4c7183 (" 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 d5d8184d ("KVM: ARM: Memory virtualization setup"). Cc: stable@vger.kernel.org # v3.9+ Fixes: d5d8184d ("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:
Shaoqin Huang <shahuang@redhat.com> Message-Id: <20230615054259.14911-1-gshan@redhat.com> Signed-off-by:
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commit afb2acb2 upstream. In kvm_vm_ioctl_create_vcpu(), add vcpu to vcpu_array iff it's safe to access vcpu via kvm_get_vcpu() and kvm_for_each_vcpu(), i.e. when there's no failure path requiring vcpu removal and destruction. Such order is important because vcpu_array accessors may end up referencing vcpu at vcpu_array[0] even before online_vcpus is set to 1. When online_vcpus=0, any call to kvm_get_vcpu() goes through array_index_nospec() and ends with an attempt to xa_load(vcpu_array, 0): int num_vcpus = atomic_read(&kvm->online_vcpus); i = array_index_nospec(i, num_vcpus); return xa_load(&kvm->vcpu_array, i); Similarly, when online_vcpus=0, a kvm_for_each_vcpu() does not iterate over an "empty" range, but actually [0, ULONG_MAX]: xa_for_each_range(&kvm->vcpu_array, idx, vcpup, 0, \ (atomic_read(&kvm->online_vcpus) - 1)) In both cases, such online_vcpus=0 edge case, even if leading to unnecessary calls to XArray API, should not be an issue; requesting unpopulated indexes/ranges is handled by xa_load() and xa_for_each_range(). However, this means that when the first vCPU is created and inserted in vcpu_array *and* before online_vcpus is incremented, code calling kvm_get_vcpu()/kvm_for_each_vcpu() already has access to that first vCPU. This should not pose a problem assuming that once a vcpu is stored in vcpu_array, it will remain there, but that's not the case: kvm_vm_ioctl_create_vcpu() first inserts to vcpu_array, then requests a file descriptor. If create_vcpu_fd() fails, newly inserted vcpu is removed from the vcpu_array, then destroyed: vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus); r = xa_insert(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, GFP_KERNEL_ACCOUNT); kvm_get_kvm(kvm); r = create_vcpu_fd(vcpu); if (r < 0) { xa_erase(&kvm->vcpu_array, vcpu->vcpu_idx); kvm_put_kvm_no_destroy(kvm); goto unlock_vcpu_destroy; } atomic_inc(&kvm->online_vcpus); This results in a possible race condition when a reference to a vcpu is acquired (via kvm_get_vcpu() or kvm_for_each_vcpu()) moments before said vcpu is destroyed. Signed-off-by:
Michal Luczaj <mhal@rbox.co> Message-Id: <20230510140410.1093987-2-mhal@rbox.co> Cc: stable@vger.kernel.org Fixes: c5b07754 ("KVM: Convert the kvm->vcpus array to a xarray", 2021-12-08) Signed-off-by:
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- Mar 10, 2023
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Sean Christopherson authored
commit 2b012812 upstream. 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:
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Sean Christopherson authored
commit b1cb1fac 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: 5d3c4c79 ("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:
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- Feb 01, 2023
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Yi Liu authored
[ Upstream commit 51cdc8bc ] Currently it is possible that the final put of a KVM reference comes from vfio during its device close operation. This occurs while the vfio group lock is held; however, if the vfio device is still in the kvm device list, then the following call chain could result in a deadlock: VFIO holds group->group_lock/group_rwsem -> kvm_put_kvm -> kvm_destroy_vm -> kvm_destroy_devices -> kvm_vfio_destroy -> kvm_vfio_file_set_kvm -> vfio_file_set_kvm -> try to hold group->group_lock/group_rwsem The key function is the kvm_destroy_devices() which triggers destroy cb of kvm_device_ops. It calls back to vfio and try to hold group_lock. So if this path doesn't call back to vfio, this dead lock would be fixed. Actually, there is a way for it. KVM provides another point to free the kvm-vfio device which is the point when the device file descriptor is closed. This can be achieved by providing the release cb instead of the destroy cb. Also rename kvm_vfio_destroy() to be kvm_vfio_release(). /* * Destroy is responsible for freeing dev. * * Destroy may be called before or after destructors are called * on emulated I/O regions, depending on whether a reference is * held by a vcpu or other kvm component that gets destroyed * after the emulated I/O. */ void (*destroy)(struct kvm_device *dev); /* * Release is an alternative method to free the device. It is * called when the device file descriptor is closed. Once * release is called, the destroy method will not be called * anymore as the device is removed from the device list of * the VM. kvm->lock is held. */ void (*release)(struct kvm_device *dev); Fixes: 421cfe65 ("vfio: remove VFIO_GROUP_NOTIFY_SET_KVM") Reported-by:
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- Nov 23, 2022
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David Woodhouse authored
In the case where a GPC is refreshed to a different location within the same page, we didn't bother to update it. Mostly we don't need to, but since the ->khva field also includes the offset within the page, that does have to be updated. Fixes: 3ba2c95e ("KVM: Do not incorporate page offset into gfn=>pfn cache user address") Signed-off-by:
David Woodhouse <dwmw@amazon.co.uk> Reviewed-by:
Paul Durrant <paul@xen.org> Reviewed-by:
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- Nov 17, 2022
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David Matlack authored
Obey kvm.halt_poll_ns in VMs not using KVM_CAP_HALT_POLL on every halt, rather than just sampling the module parameter when the VM is first created. This restore the original behavior of kvm.halt_poll_ns for VMs that have not opted into KVM_CAP_HALT_POLL. Notably, this change restores the ability for admins to disable or change the maximum halt-polling time system wide for VMs not using KVM_CAP_HALT_POLL. Reported-by:
Christian Borntraeger <borntraeger@de.ibm.com> Fixes: acd05785 ("kvm: add capability for halt polling") Signed-off-by:
David Matlack <dmatlack@google.com> Message-Id: <20221117001657.1067231-4-dmatlack@google.com> Signed-off-by:
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David Matlack authored
Avoid re-reading kvm->max_halt_poll_ns multiple times during halt-polling except when it is explicitly useful, e.g. to check if the max time changed across a halt. kvm->max_halt_poll_ns can be changed at any time by userspace via KVM_CAP_HALT_POLL. This bug is unlikely to cause any serious side-effects. In the worst case one halt polls for shorter or longer than it should, and then is fixed up on the next halt. Furthmore, this is still possible since kvm->max_halt_poll_ns are not synchronized with halts. Fixes: acd05785 ("kvm: add capability for halt polling") Signed-off-by:
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David Matlack authored
Cap vcpu->halt_poll_ns based on the max halt polling time just before halting, rather than after the last halt. This arguably provides better accuracy if an admin disables halt polling in between halts, although the improvement is nominal. A side-effect of this change is that grow_halt_poll_ns() no longer needs to access vcpu->kvm->max_halt_poll_ns, which will be useful in a future commit where the max halt polling time can come from the module parameter halt_poll_ns instead. Signed-off-by:
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- Oct 31, 2022
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Gavin Shan authored
There are two capabilities related to ring-based dirty page tracking: KVM_CAP_DIRTY_LOG_RING and KVM_CAP_DIRTY_LOG_RING_ACQ_REL. Both are supported by x86. However, arm64 supports KVM_CAP_DIRTY_LOG_RING_ACQ_REL only when the feature is supported on arm64. The userspace doesn't have to enable the advertised capability, meaning KVM_CAP_DIRTY_LOG_RING can be enabled on arm64 by userspace and it's wrong. Fix it by double checking if the capability has been advertised prior to enabling it. It's rejected to enable the capability if it hasn't been advertised. Fixes: 17601bfe ("KVM: Add KVM_CAP_DIRTY_LOG_RING_ACQ_REL capability and config option") Reported-by:
Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20221031003621.164306-4-gshan@redhat.com
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- Oct 27, 2022
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Sean Christopherson authored
Reject kvm_gpc_check() and kvm_gpc_refresh() if the cache is inactive. Not checking the active flag during refresh is particularly egregious, as KVM can end up with a valid, inactive cache, which can lead to a variety of use-after-free bugs, e.g. consuming a NULL kernel pointer or missing an mmu_notifier invalidation due to the cache not being on the list of gfns to invalidate. Note, "active" needs to be set if and only if the cache is on the list of caches, i.e. is reachable via mmu_notifier events. If a relevant mmu_notifier event occurs while the cache is "active" but not on the list, KVM will not acquire the cache's lock and so will not serailize the mmu_notifier event with active users and/or kvm_gpc_refresh(). A race between KVM_XEN_ATTR_TYPE_SHARED_INFO and KVM_XEN_HVM_EVTCHN_SEND can be exploited to trigger the bug. 1. Deactivate shinfo cache: kvm_xen_hvm_set_attr case KVM_XEN_ATTR_TYPE_SHARED_INFO kvm_gpc_deactivate kvm_gpc_unmap gpc->valid = false gpc->khva = NULL gpc->active = false Result: active = false, valid = false 2. Cause cache refresh: kvm_arch_vm_ioctl case KVM_XEN_HVM_EVTCHN_SEND kvm_xen_hvm_evtchn_send kvm_xen_set_evtchn kvm_xen_set_evtchn_fast kvm_gpc_check return -EWOULDBLOCK because !gpc->valid kvm_xen_set_evtchn_fast return -EWOULDBLOCK kvm_gpc_refresh hva_to_pfn_retry gpc->valid = true gpc->khva = not NULL Result: active = false, valid = true 3. Race ioctl KVM_XEN_HVM_EVTCHN_SEND against ioctl KVM_XEN_ATTR_TYPE_SHARED_INFO: kvm_arch_vm_ioctl case KVM_XEN_HVM_EVTCHN_SEND kvm_xen_hvm_evtchn_send kvm_xen_set_evtchn kvm_xen_set_evtchn_fast read_lock gpc->lock kvm_xen_hvm_set_attr case KVM_XEN_ATTR_TYPE_SHARED_INFO mutex_lock kvm->lock kvm_xen_shared_info_init kvm_gpc_activate gpc->khva = NULL kvm_gpc_check [ Check passes because gpc->valid is still true, even though gpc->khva is already NULL. ] shinfo = gpc->khva pending_bits = shinfo->evtchn_pending CRASH: test_and_set_bit(..., pending_bits) Fixes: 982ed0de ("KVM: Reinstate gfn_to_pfn_cache with invalidation support") Cc: stable@vger.kernel.org Reported-by: -
Michal Luczaj authored
Move the gfn_to_pfn_cache lock initialization to another helper and call the new helper during VM/vCPU creation. There are race conditions possible due to kvm_gfn_to_pfn_cache_init()'s ability to re-initialize the cache's locks. For example: a race between ioctl(KVM_XEN_HVM_EVTCHN_SEND) and kvm_gfn_to_pfn_cache_init() leads to a corrupted shinfo gpc lock. (thread 1) | (thread 2) | kvm_xen_set_evtchn_fast | read_lock_irqsave(&gpc->lock, ...) | | kvm_gfn_to_pfn_cache_init | rwlock_init(&gpc->lock) read_unlock_irqrestore(&gpc->lock, ...) | Rename "cache_init" and "cache_destroy" to activate+deactivate to avoid implying that the cache really is destroyed/freed. Note, there more races in the newly named kvm_gpc_activate() that will be addressed separately. Fixes: 982ed0de ("KVM: Reinstate gfn_to_pfn_cache with invalidation support") Cc: stable@vger.kernel.org Suggested-by: -
Hou Wenlong authored
Although simple_attr_open() fails only with -ENOMEM with current code base, it would be nicer to return retval of simple_attr_open() directly in kvm_debugfs_open(). No functional change intended. Signed-off-by:
Hou Wenlong <houwenlong.hwl@antgroup.com> Message-Id: <69d64d93accd1f33691b8a383ae555baee80f943.1665975828.git.houwenlong.hwl@antgroup.com> Cc: stable@vger.kernel.org Signed-off-by:
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- Oct 22, 2022
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Alexander Graf authored
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:
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- Oct 07, 2022
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Jason Gunthorpe authored
SPAPR exists completely outside the normal iommu driver framework, the groups it creates are fake and are only created to enable VFIO's uAPI. Thus, it does not need to follow the iommu core rule that the iommu_group will only be touched while a driver is attached. Carry a group reference into KVM and have KVM directly manage the lifetime of this object independently of VFIO. This means KVM no longer relies on the vfio group file being valid to maintain the group reference. Tested-by:
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Jason Gunthorpe authored
This replaces uses of vfio_file_iommu_group() which were only detecting if the file is a VFIO file with no interest in the actual group. The only remaning user of vfio_file_iommu_group() is in KVM for the SPAPR stuff. It passes the iommu_group into the arch code through kvm for some reason. Tested-by:
Eric Farman <farman@linux.ibm.com> Signed-off-by:
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- Sep 29, 2022
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Marc Zyngier authored
In order to differenciate between architectures that require no extra synchronisation when accessing the dirty ring and those who do, add a new capability (KVM_CAP_DIRTY_LOG_RING_ACQ_REL) that identify the latter sort. TSO architectures can obviously advertise both, while relaxed architectures must only advertise the ACQ_REL version. This requires some configuration symbol rejigging, with HAVE_KVM_DIRTY_RING being only indirectly selected by two top-level config symbols: - HAVE_KVM_DIRTY_RING_TSO for strongly ordered architectures (x86) - HAVE_KVM_DIRTY_RING_ACQ_REL for weakly ordered architectures (arm64) Suggested-by:
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Marc Zyngier authored
The current implementation of the dirty ring has an implicit requirement that stores to the dirty ring from userspace must be: - be ordered with one another - visible from another CPU executing a ring reset While these implicit requirements work well for x86 (and any other TSO-like architecture), they do not work for more relaxed architectures such as arm64 where stores to different addresses can be freely reordered, and loads from these addresses not observing writes from another CPU unless the required barriers (or acquire/release semantics) are used. In order to start fixing this, upgrade the ring reset accesses: - the kvm_dirty_gfn_harvested() helper now uses acquire semantics so it is ordered after all previous writes, including that from userspace - the kvm_dirty_gfn_set_invalid() helper now uses release semantics so that the next_slot and next_offset reads don't drift past the entry invalidation This is only a partial fix as the userspace side also need upgrading. Signed-off-by:
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- Sep 26, 2022
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Paolo Bonzini authored
KVM_REQ_UNHALT is now unnecessary because it is replaced by the return value of kvm_vcpu_block/kvm_vcpu_halt. Remove it. No functional change intended. Signed-off-by:
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Miaohe Lin authored
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: baff59cc ("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:
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- Aug 19, 2022
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Li kunyu authored
The variable is initialized but it is only used after its assignment. Reviewed-by:
Li kunyu <kunyu@nfschina.com> Message-Id: <20220819021535.483702-1-kunyu@nfschina.com> Signed-off-by:
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Li kunyu authored
The variable is initialized but it is only used after its assignment. Reviewed-by:
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Chao Peng authored
The motivation of this renaming is to make these variables and related helper functions less mmu_notifier bound and can also be used for non mmu_notifier based page invalidation. mmu_invalidate_* was chosen to better describe the purpose of 'invalidating' a page that those variables are used for. - mmu_notifier_seq/range_start/range_end are renamed to mmu_invalidate_seq/range_start/range_end. - mmu_notifier_retry{_hva} helper functions are renamed to mmu_invalidate_retry{_hva}. - mmu_notifier_count is renamed to mmu_invalidate_in_progress to avoid confusion with mn_active_invalidate_count. - While here, also update kvm_inc/dec_notifier_count() to kvm_mmu_invalidate_begin/end() to match the change for mmu_notifier_count. No functional change intended. Signed-off-by:Chao Peng <chao.p.peng@linux.intel.com> Message-Id: <20220816125322.1110439-3-chao.p.peng@linux.intel.com> Signed-off-by:
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Sean Christopherson authored
Invoke kvm_coalesced_mmio_init() from kvm_create_vm() now that allocating and initializing coalesced MMIO objects is separate from registering any associated devices. Moving coalesced MMIO cleans up the last oddity where KVM does VM creation/initialization after kvm_create_vm(), and more importantly after kvm_arch_post_init_vm() is called and the VM is added to the global vm_list, i.e. after the VM is fully created as far as KVM is concerned. Originally, kvm_coalesced_mmio_init() was called by kvm_create_vm(), but the original implementation was completely devoid of error handling. Commit 6ce5a090 ("KVM: coalesced_mmio: fix kvm_coalesced_mmio_init()'s error handling" fixed the various bugs, and in doing so rightly moved the call to after kvm_create_vm() because kvm_coalesced_mmio_init() also registered the coalesced MMIO device. Commit 2b3c246a ("KVM: Make coalesced mmio use a device per zone") cleaned up that mess by having each zone register a separate device, i.e. moved device registration to its logical home in kvm_vm_ioctl_register_coalesced_mmio(). As a result, kvm_coalesced_mmio_init() is now a "pure" initialization helper and can be safely called from kvm_create_vm(). Opportunstically drop the #ifdef, KVM provides stubs for kvm_coalesced_mmio_{init,free}() when CONFIG_KVM_MMIO=n (s390). Signed-off-by:
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Sean Christopherson authored
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 3f2b9c9c ("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: 5f6de5cb ("KVM: Prevent module exit until all VMs are freed") Cc: stable@vger.kernel.org Cc: David Matlack <dmatlack@google.com> Signed-off-by:
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Sean Christopherson authored
Properly unwind VM creation if kvm_create_vm_debugfs() fails. A recent change to invoke kvm_create_vm_debug() in kvm_create_vm() was led astray by buggy try_get_module() handling adding by commit 5f6de5cb ("KVM: Prevent module exit until all VMs are freed"). The debugfs error path effectively inherits the bad error path of try_module_get(), e.g. KVM leaves the to-be-free VM on vm_list even though KVM appears to do the right thing by calling module_put() and falling through. Opportunistically hoist kvm_create_vm_debugfs() above the call to kvm_arch_post_init_vm() so that the "post-init" arch hook is actually invoked after the VM is initialized (ignoring kvm_coalesced_mmio_init() for the moment). x86 is the only non-nop implementation of the post-init hook, and it doesn't allocate/initialize any objects that are reachable via debugfs code (spawns a kthread worker for the NX huge page mitigation). Leave the buggy try_get_module() alone for now, it will be fixed in a separate commit. Fixes: b74ed7a6 ("KVM: Actually create debugfs in kvm_create_vm()") Reported-by:
<syzbot+744e173caec2e1627ee0@syzkaller.appspotmail.com> Cc: Oliver Upton <oliver.upton@linux.dev> Signed-off-by:
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- Aug 10, 2022
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Oliver Upton authored
Doing debugfs creation after vm creation leaves things in a quasi-initialized state for a while. This is further complicated by the fact that we tear down debugfs from kvm_destroy_vm(). Align debugfs and stats init/destroy with the vm init/destroy pattern to avoid any headaches. Note the fix for a benign mistake in error handling for calls to kvm_arch_create_vm_debugfs() rolled in. Since all implementations of the function return 0 unconditionally it isn't actually a bug at the moment. Lastly, tear down debugfs/stats data in the kvm_create_vm_debugfs() error path. Previously it was safe to assume that kvm_destroy_vm() would take out the garbage, that is no longer the case. Signed-off-by:
Oliver Upton <oupton@google.com> Message-Id: <20220720092259.3491733-6-oliver.upton@linux.dev> Signed-off-by:
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Oliver Upton authored
At the time the VM fd is used in kvm_create_vm_debugfs(), the fd has been allocated but not yet installed. It is only really useful as an identifier in strings for the VM (such as debugfs). Treat it exactly as such by passing the string name of the fd to kvm_create_vm_debugfs(), futureproofing against possible misuse of the VM fd. Suggested-by:
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Oliver Upton authored
Allocate a VM's fd at the very beginning of kvm_dev_ioctl_create_vm() so that KVM can use the fd value to generate strigns, e.g. for debugfs, when creating and initializing the VM. Signed-off-by:
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Oliver Upton authored
Initialize stats_id alongside other kvm_vcpu fields to make it more difficult to unintentionally access stats_id before it's set. No functional change intended. Signed-off-by:
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Oliver Upton authored
Initialize stats_id alongside other struct kvm fields to make it more difficult to unintentionally access stats_id before it's set. While at it, move the format string to the first line of the call and fix the indentation of the second line. No functional change intended. Signed-off-by:
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- Jul 29, 2022
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Anup Patel authored
The kvm_mmu_topup_memory_cache() always uses GFP_KERNEL_ACCOUNT for memory allocation which prevents it's use in atomic context. To address this limitation of kvm_mmu_topup_memory_cache(), we add gfp_custom flag in struct kvm_mmu_memory_cache. When the gfp_custom flag is set to some GFP_xyz flags, the kvm_mmu_topup_memory_cache() will use that instead of GFP_KERNEL_ACCOUNT. Signed-off-by:
Anup Patel <apatel@ventanamicro.com> Reviewed-by:
Atish Patra <atishp@rivosinc.com> Signed-off-by:
Anup Patel <anup@brainfault.org>
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- Jun 24, 2022
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Vineeth Pillai authored
Add a new debugfs file to expose the pid of each vcpu threads. This is very helpful for userland tools to get the vcpu pids without worrying about thread naming conventions of the VMM. Signed-off-by:
Vineeth Pillai (Google) <vineeth@bitbyteword.org> Message-Id: <20220523190327.2658-1-vineeth@bitbyteword.org> Signed-off-by:
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David Matlack authored
Allow the capacity of the kvm_mmu_memory_cache struct to be chosen at declaration time rather than being fixed for all declarations. This will be used in a follow-up commit to declare an cache in x86 with a capacity of 512+ objects without having to increase the capacity of all caches in KVM. This change requires each cache now specify its capacity at runtime, since the cache struct itself no longer has a fixed capacity known at compile time. To protect against someone accidentally defining a kvm_mmu_memory_cache struct directly (without the extra storage), this commit includes a WARN_ON() in kvm_mmu_topup_memory_cache(). In order to support different capacities, this commit changes the objects pointer array to be dynamically allocated the first time the cache is topped-up. While here, opportunistically clean up the stack-allocated kvm_mmu_memory_cache structs in riscv and arm64 to use designated initializers. No functional change intended. Reviewed-by:
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- Jun 20, 2022
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Sean Christopherson authored
Drop the unnecessary initialization of the local 'pfn' variable in hva_to_pfn(). First and foremost, '0' is not an invalid pfn, it's a perfectly valid pfn on most architectures. I.e. if hva_to_pfn() were to return an "uninitializd" pfn, it would actually be interpeted as a legal pfn by most callers. Second, hva_to_pfn() can't return an uninitialized pfn as hva_to_pfn() explicitly sets pfn to an error value (or returns an error value directly) if a helper returns failure, and all helpers set the pfn on success. The zeroing of 'pfn' was introduced by commit 2fc84311 ("KVM: reorganize hva_to_pfn"), probably to avoid "uninitialized variable" warnings on statements that return pfn. However, no compiler seems to produce them, making the initialization unnecessary. Signed-off-by:
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