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  1. Mar 03, 2021
  3. Feb 26, 2021
  5. Feb 25, 2021
    • Sean Christopherson's avatar
      KVM: SVM: Fix nested VM-Exit on #GP interception handling · 2df8d380
      Sean Christopherson authored 
      Fix the interpreation of nested_svm_vmexit()'s return value when
synthesizing a nested VM-Exit after intercepting an SVM instruction while
L2 was running.  The helper returns '0' on success, whereas a return
value of '0' in the exit handler path means "exit to userspace".  The
incorrect return value causes KVM to exit to userspace without filling
the run state, e.g. QEMU logs "KVM: unknown exit, hardware reason 0".

Fixes: 14c2bf81

 ("KVM: SVM: Fix #GP handling for doubly-nested virtualization")
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210224005627.657028-1-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      2df8d380
  7. Feb 24, 2021
  9. Feb 23, 2021
    • David Stevens's avatar
      KVM: x86/mmu: Consider the hva in mmu_notifier retry · 4a42d848
      David Stevens authored 
      

Track the range being invalidated by mmu_notifier and skip page fault
retries if the fault address is not affected by the in-progress
invalidation. Handle concurrent invalidations by finding the minimal
range which includes all ranges being invalidated. Although the combined
range may include unrelated addresses and cannot be shrunk as individual
invalidation operations complete, it is unlikely the marginal gains of
proper range tracking are worth the additional complexity.

The primary benefit of this change is the reduction in the likelihood of
extreme latency when handing a page fault due to another thread having
been preempted while modifying host virtual addresses.

Signed-off-by: default avatarDavid Stevens <stevensd@chromium.org>
Message-Id: <20210222024522.1751719-3-stevensd@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      4a42d848
    • Sean Christopherson's avatar
      KVM: x86/mmu: Skip mmu_notifier check when handling MMIO page fault · 5f8a7cf2
      Sean Christopherson authored 
      

Don't retry a page fault due to an mmu_notifier invalidation when
handling a page fault for a GPA that did not resolve to a memslot, i.e.
an MMIO page fault.  Invalidations from the mmu_notifier signal a change
in a host virtual address (HVA) mapping; without a memslot, there is no
HVA and thus no possibility that the invalidation is relevant to the
page fault being handled.

Note, the MMIO vs. memslot generation checks handle the case where a
pending memslot will create a memslot overlapping the faulting GPA.  The
mmu_notifier checks are orthogonal to memslot updates.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210222024522.1751719-2-stevensd@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      5f8a7cf2
    • Lukas Bulwahn's avatar
      KVM: Documentation: rectify rst markup in KVM_GET_SUPPORTED_HV_CPUID · 356c7558
      Lukas Bulwahn authored 
      Commit c21d54f0

 ("KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID
as a system ioctl") added an enumeration in the KVM_GET_SUPPORTED_HV_CPUID
documentation improperly for rst, and caused new warnings in make htmldocs:

  Documentation/virt/kvm/api.rst:4536: WARNING: Unexpected indentation.
  Documentation/virt/kvm/api.rst:4538: WARNING: Block quote ends without a blank line; unexpected unindent.

Fix that issue and another historic rst markup issue from the initial
rst conversion in the KVM_GET_SUPPORTED_HV_CPUID documentation.

Signed-off-by: default avatarLukas Bulwahn <lukas.bulwahn@gmail.com>
Message-Id: <20210104095938.24838-1-lukas.bulwahn@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      356c7558
    • Paolo Bonzini's avatar
      KVM: nSVM: prepare guest save area while is_guest_mode is true · d2df592f
      Paolo Bonzini authored 
      Right now, enter_svm_guest_mode is calling nested_prepare_vmcb_save and
nested_prepare_vmcb_control.  This results in is_guest_mode being false
until the end of nested_prepare_vmcb_control.

This is a problem because nested_prepare_vmcb_save can in turn cause
changes to the intercepts and these have to be applied to the "host VMCB"
(stored in svm->nested.hsave) and then merged with the VMCB12 intercepts
into svm->vmcb.

In particular, without this change we forget to set the CR0 read and CR0
write intercepts when running a real mode L2 guest with NPT disabled.
The guest is therefore able to see the CR0.PG bit that KVM sets to
enable "paged real mode".  This patch fixes the svm.flat mode_switch
test case with npt=0.  There are no other problematic calls in
nested_prepare_vmcb_save.

Moving is_guest_mode to the end is done since commit 06fc7772
("KVM: SVM: Activate nested state only when guest state is complete",
2010-04-25).  However, back then KVM didn't grab a different VMCB
when updating the intercepts, it had already copied/merged L1's stuff
to L0's VMCB, and then updated L0's VMCB regardless of is_nested().
Later recalc_intercepts was introduced in commit 384c6368
("KVM: SVM: Add function to recalculate intercept masks", 2011-01-12).
This introduced the bug, because recalc_intercepts now throws away
the intercept manipulations that svm_set_cr0 had done in the meanwhile
to svm->vmcb.

[1] https://lore.kernel.org/kvm/1266493115-28386-1-git-send-email-joerg.roedel@amd.com/



Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Tested-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      d2df592f
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