From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
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: Jim Mattson <jmattson@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5d903f8909d1..1b3ca0582a0c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6107,28 +6107,21 @@ static void vmx_apicv_post_state_restore(struct kvm_vcpu *vcpu)
static void vmx_complete_atomic_exit(struct vcpu_vmx *vmx)
{
- u32 exit_intr_info = 0;
- u16 basic_exit_reason = (u16)vmx->exit_reason;
-
- if (!(basic_exit_reason == EXIT_REASON_MCE_DURING_VMENTRY
- || basic_exit_reason == EXIT_REASON_EXCEPTION_NMI))
+ if (vmx->exit_reason != EXIT_REASON_EXCEPTION_NMI)
return;
- if (!(vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
- exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
- vmx->exit_intr_info = exit_intr_info;
+ vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
/* if exit due to PF check for async PF */
- if (is_page_fault(exit_intr_info))
+ if (is_page_fault(vmx->exit_intr_info))
vmx->vcpu.arch.apf.host_apf_reason = kvm_read_and_reset_pf_reason();
/* Handle machine checks before interrupts are enabled */
- if (basic_exit_reason == EXIT_REASON_MCE_DURING_VMENTRY ||
- is_machine_check(exit_intr_info))
+ if (is_machine_check(vmx->exit_intr_info))
kvm_machine_check();
/* We need to handle NMIs before interrupts are enabled */
- if (is_nmi(exit_intr_info)) {
+ if (is_nmi(vmx->exit_intr_info)) {
kvm_before_interrupt(&vmx->vcpu);
asm("int $2");
kvm_after_interrupt(&vmx->vcpu);
@@ -6535,6 +6528,9 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx->idt_vectoring_info = 0;
vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON);
+ if ((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY)
+ kvm_machine_check();
+
if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
return;
--
1.8.3.1
