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KVM: nVMX: Prioritize TSS T-flag #DBs over Monitor Trap Flag

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Service TSS T-flag #DBs prior to pending MTFs, as such #DBs are higher
priority than MTF.  KVM itself doesn't emulate TSS #DBs, and any such
exceptions injected from L1 will be handled by hardware (or morphed to
a fault-like exception if injection fails), but theoretically userspace
could pend a TSS T-flag #DB in conjunction with a pending MTF.

Note, there's no known use case this fixes, it's purely to be technically
correct with respect to Intel's SDM.

Cc: Oliver Upton <oupton@google.com>
Cc: Peter Shier <pshier@google.com>
Fixes: 5ef8acbdd687 ("KVM: nVMX: Emulate MTF when performing instruction emulation")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-8-seanjc@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-08-30 23:15:54 +00:00 committed by Paolo Bonzini
parent 8d178f4607
commit b9d44f9091
1 changed files with 5 additions and 3 deletions
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8
arch/x86/kvm/vmx/nested.c
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@ -3985,15 +3985,17 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
}
/*
* Process any exceptions that are not debug traps before MTF.
* Process exceptions that are higher priority than Monitor Trap Flag:
* fault-like exceptions, TSS T flag #DB (not emulated by KVM, but
* could theoretically come in from userspace), and ICEBP (INT1).
*
* Note that only a pending nested run can block a pending exception.
* Otherwise an injected NMI/interrupt should either be
* lost or delivered to the nested hypervisor in the IDT_VECTORING_INFO,
* while delivering the pending exception.
*/
if (vcpu->arch.exception.pending && !vmx_get_pending_dbg_trap(vcpu)) {
if (vcpu->arch.exception.pending &&
!(vmx_get_pending_dbg_trap(vcpu) & ~DR6_BT)) {
if (vmx->nested.nested_run_pending)
return -EBUSY;
if (!nested_vmx_check_exception(vcpu, &exit_qual))