lwn.git/virt/kvm/async_pf.c, branch docs-5.15-2

mm/gup: remove task_struct pointer for all gup code

2020-08-12T17:58:04+00:00

After the cleanup of page fault accounting, gup does not need to pass task_struct around any more. Remove that parameter in the whole gup stack. Signed-off-by: Peter Xu Signed-off-by: Andrew Morton Reviewed-by: John Hubbard Link: http://lkml.kernel.org/r/20200707225021.200906-26-peterx@redhat.com Signed-off-by: Linus Torvalds

KVM: async_pf: change kvm_setup_async_pf()/kvm_arch_setup_async_pf() return type to bool

2020-07-08T20:21:36+00:00

Unlike normal 'int' functions returning '0' on success, kvm_setup_async_pf()/ kvm_arch_setup_async_pf() return '1' when a job to handle page fault asynchronously was scheduled and '0' otherwise. To avoid the confusion change return type to 'bool'. No functional change intended. Suggested-by: Sean Christopherson Signed-off-by: Vitaly Kuznetsov Message-Id: <20200615121334.91300-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2020-06-12T18:05:52+00:00

Pull more KVM updates from Paolo Bonzini: "The guest side of the asynchronous page fault work has been delayed to 5.9 in order to sync with Thomas's interrupt entry rework, but here's the rest of the KVM updates for this merge window. MIPS: - Loongson port PPC: - Fixes ARM: - Fixes x86: - KVM_SET_USER_MEMORY_REGION optimizations - Fixes - Selftest fixes" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (62 commits) KVM: x86: do not pass poisoned hva to __kvm_set_memory_region KVM: selftests: fix sync_with_host() in smm_test KVM: async_pf: Inject 'page ready' event only if 'page not present' was previously injected KVM: async_pf: Cleanup kvm_setup_async_pf() kvm: i8254: remove redundant assignment to pointer s KVM: x86: respect singlestep when emulating instruction KVM: selftests: Don't probe KVM_CAP_HYPERV_ENLIGHTENED_VMCS when nested VMX is unsupported KVM: selftests: do not substitute SVM/VMX check with KVM_CAP_NESTED_STATE check KVM: nVMX: Consult only the "basic" exit reason when routing nested exit KVM: arm64: Move hyp_symbol_addr() to kvm_asm.h KVM: arm64: Synchronize sysreg state on injecting an AArch32 exception KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts KVM: arm64: Remove host_cpu_context member from vcpu structure KVM: arm64: Stop sparse from moaning at __hyp_this_cpu_ptr KVM: arm64: Handle PtrAuth traps early KVM: x86: Unexport x86_fpu_cache and make it static KVM: selftests: Ignore KVM 5-level paging support for VM_MODE_PXXV48_4K KVM: arm64: Save the host's PtrAuth keys in non-preemptible context KVM: arm64: Stop save/restoring ACTLR_EL1 KVM: arm64: Add emulation for 32bit guests accessing ACTLR2 ...

KVM: async_pf: Inject 'page ready' event only if 'page not present' was previously injected

2020-06-11T16:35:19+00:00

'Page not present' event may or may not get injected depending on guest's state. If the event wasn't injected, there is no need to inject the corresponding 'page ready' event as the guest may get confused. E.g. Linux thinks that the corresponding 'page not present' event wasn't delivered *yet* and allocates a 'dummy entry' for it. This entry is never freed. Note, 'wakeup all' events have no corresponding 'page not present' event and always get injected. s390 seems to always be able to inject 'page not present', the change is effectively a nop. Suggested-by: Vivek Goyal Signed-off-by: Vitaly Kuznetsov Message-Id: <20200610175532.779793-2-vkuznets@redhat.com> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=208081 Signed-off-by: Paolo Bonzini

KVM: async_pf: Cleanup kvm_setup_async_pf()

2020-06-11T16:35:19+00:00

schedule_work() returns 'false' only when the work is already on the queue and this can't happen as kvm_setup_async_pf() always allocates a new one. Also, to avoid potential race, it makes sense to to schedule_work() at the very end after we've added it to the queue. While on it, do some minor cleanup. gfn_to_pfn_async() mentioned in a comment does not currently exist and, moreover, we can check kvm_is_error_hva() at the very beginning, before we try to allocate work so 'retry_sync' label can go away completely. Signed-off-by: Vitaly Kuznetsov Message-Id: <20200610175532.779793-1-vkuznets@redhat.com> Reviewed-by: Sean Christopherson Signed-off-by: Paolo Bonzini

mmap locking API: use coccinelle to convert mmap_sem rwsem call sites

2020-06-09T16:39:14+00:00

This change converts the existing mmap_sem rwsem calls to use the new mmap locking API instead. The change is generated using coccinelle with the following rule: // spatch --sp-file mmap_lock_api.cocci --in-place --include-headers --dir . @@ expression mm; @@ ( -init_rwsem +mmap_init_lock | -down_write +mmap_write_lock | -down_write_killable +mmap_write_lock_killable | -down_write_trylock +mmap_write_trylock | -up_write +mmap_write_unlock | -downgrade_write +mmap_write_downgrade | -down_read +mmap_read_lock | -down_read_killable +mmap_read_lock_killable | -down_read_trylock +mmap_read_trylock | -up_read +mmap_read_unlock ) -(&mm->mmap_sem) +(mm) Signed-off-by: Michel Lespinasse Signed-off-by: Andrew Morton Reviewed-by: Daniel Jordan Reviewed-by: Laurent Dufour Reviewed-by: Vlastimil Babka Cc: Davidlohr Bueso Cc: David Rientjes Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: Jerome Glisse Cc: John Hubbard Cc: Liam Howlett Cc: Matthew Wilcox Cc: Peter Zijlstra Cc: Ying Han Link: http://lkml.kernel.org/r/20200520052908.204642-5-walken@google.com Signed-off-by: Linus Torvalds

KVM: x86: acknowledgment mechanism for async pf page ready notifications

2020-06-01T08:26:08+00:00

If two page ready notifications happen back to back the second one is not delivered and the only mechanism we currently have is kvm_check_async_pf_completion() check in vcpu_run() loop. The check will only be performed with the next vmexit when it happens and in some cases it may take a while. With interrupt based page ready notification delivery the situation is even worse: unlike exceptions, interrupts are not handled immediately so we must check if the slot is empty. This is slow and unnecessary. Introduce dedicated MSR_KVM_ASYNC_PF_ACK MSR to communicate the fact that the slot is free and host should check its notification queue. Mandate using it for interrupt based 'page ready' APF event delivery. As kvm_check_async_pf_completion() is going away from vcpu_run() we need a way to communicate the fact that vcpu->async_pf.done queue has transitioned from empty to non-empty state. Introduce kvm_arch_async_page_present_queued() and KVM_REQ_APF_READY to do the job. Signed-off-by: Vitaly Kuznetsov Message-Id: <20200525144125.143875-7-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini

KVM: rename kvm_arch_can_inject_async_page_present() to kvm_arch_can_dequeue_async_page_present()

2020-06-01T08:26:07+00:00

An innocent reader of the following x86 KVM code: bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu) { if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED)) return true; ... may get very confused: if APF mechanism is not enabled, why do we report that we 'can inject async page present'? In reality, upon injection kvm_arch_async_page_present() will check the same condition again and, in case APF is disabled, will just drop the item. This is fine as the guest which deliberately disabled APF doesn't expect to get any APF notifications. Rename kvm_arch_can_inject_async_page_present() to kvm_arch_can_dequeue_async_page_present() to make it clear what we are checking: if the item can be dequeued (meaning either injected or just dropped). On s390 kvm_arch_can_inject_async_page_present() always returns 'true' so the rename doesn't matter much. Signed-off-by: Vitaly Kuznetsov Message-Id: <20200525144125.143875-4-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini

kvm: Replace vcpu->swait with rcuwait

2020-05-13T16:14:56+00:00

The use of any sort of waitqueue (simple or regular) for wait/waking vcpus has always been an overkill and semantically wrong. Because this is per-vcpu (which is blocked) there is only ever a single waiting vcpu, thus no need for any sort of queue. As such, make use of the rcuwait primitive, with the following considerations: - rcuwait already provides the proper barriers that serialize concurrent waiter and waker. - Task wakeup is done in rcu read critical region, with a stable task pointer. - Because there is no concurrency among waiters, we need not worry about rcuwait_wait_event() calls corrupting the wait->task. As a consequence, this saves the locking done in swait when modifying the queue. This also applies to per-vcore wait for powerpc kvm-hv. The x86 tscdeadline_latency test mentioned in 8577370fb0cb ("KVM: Use simple waitqueue for vcpu->wq") shows that, on avg, latency is reduced by around 15-20% with this change. Cc: Paul Mackerras Cc: kvmarm@lists.cs.columbia.edu Cc: linux-mips@vger.kernel.org Reviewed-by: Marc Zyngier Signed-off-by: Davidlohr Bueso Message-Id: <20200424054837.5138-6-dave@stgolabs.net> [Avoid extra logic changes. - Paolo] Signed-off-by: Paolo Bonzini

KVM: async_pf: drop kvm_arch_async_page_present wrappers

2020-01-23T08:51:08+00:00

The wrappers make it less clear that the position of the call to kvm_arch_async_page_present depends on the architecture, and that only one of the two call sites will actually be active. Remove them. Cc: Andy Lutomirski Cc: Christian Borntraeger Signed-off-by: Paolo Bonzini