KVM: VMX: Fix handling of #MC that occurs during VM-Entry
authorSean Christopherson <sean.j.christopherson@intel.com>
Sat, 20 Apr 2019 05:50:55 +0000 (22:50 -0700)
committerPaolo Bonzini <pbonzini@redhat.com>
Tue, 18 Jun 2019 09:45:44 +0000 (11:45 +0200)
commitbeb8d93b3e423043e079ef3dda19dad7b28467a8
tree0ce2395cda563a990a78e11fb78dd72030f0f0b5
parent73f624f47c495d7129abef4b7031ed371cc7abb6
KVM: VMX: Fix handling of #MC that occurs during VM-Entry

A previous fix to prevent KVM from consuming stale VMCS state after a
failed VM-Entry inadvertantly blocked KVM's handling of machine checks
that occur during VM-Entry.

Per Intel's SDM, a #MC during VM-Entry is handled in one of three ways,
depending on when the #MC is recognoized.  As it pertains to this bug
fix, the third case explicitly states EXIT_REASON_MCE_DURING_VMENTRY
is handled like any other VM-Exit during VM-Entry, i.e. sets bit 31 to
indicate the VM-Entry failed.

If a machine-check event occurs during a VM entry, one of the following occurs:
 - The machine-check event is handled as if it occurred before the VM entry:
        ...
 - The machine-check event is handled after VM entry completes:
        ...
 - A VM-entry failure occurs as described in Section 26.7. The basic
   exit reason is 41, for "VM-entry failure due to machine-check event".

Explicitly handle EXIT_REASON_MCE_DURING_VMENTRY as a one-off case in
vmx_vcpu_run() instead of binning it into vmx_complete_atomic_exit().
Doing so allows vmx_vcpu_run() to handle VMX_EXIT_REASONS_FAILED_VMENTRY
in a sane fashion and also simplifies vmx_complete_atomic_exit() since
VMCS.VM_EXIT_INTR_INFO is guaranteed to be fresh.

Fixes: b060ca3b2e9e7 ("kvm: vmx: Handle VMLAUNCH/VMRESUME failure properly")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
arch/x86/kvm/vmx/vmx.c