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KVM: nVMX: Handle pending #DB when injecting INIT VM-exit

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SDM 27.3.4 states that the 'pending debug exceptions' VMCS field will
be populated if a VM-exit caused by an INIT signal takes priority over a
debug-trap. Emulate this behavior when synthesizing an INIT signal
VM-exit into L1.

Fixes: 4b9852f4f3 ("KVM: x86: Fix INIT signal handling in various CPU states")
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Oliver Upton 2020-02-07 02:36:05 -08:00 committed by Paolo Bonzini
parent 307f1cfa26
commit 684c0422da
1 changed files with 28 additions and 0 deletions
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28
arch/x86/kvm/vmx/nested.c
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@ -3575,6 +3575,33 @@ static void nested_vmx_inject_exception_vmexit(struct kvm_vcpu *vcpu,
nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI, intr_info, exit_qual);
}
/*
* Returns true if a debug trap is pending delivery.
*
* In KVM, debug traps bear an exception payload. As such, the class of a #DB
* exception may be inferred from the presence of an exception payload.
*/
static inline bool vmx_pending_dbg_trap(struct kvm_vcpu *vcpu)
{
return vcpu->arch.exception.pending &&
vcpu->arch.exception.nr == DB_VECTOR &&
vcpu->arch.exception.payload;
}
/*
* Certain VM-exits set the 'pending debug exceptions' field to indicate a
* recognized #DB (data or single-step) that has yet to be delivered. Since KVM
* represents these debug traps with a payload that is said to be compatible
* with the 'pending debug exceptions' field, write the payload to the VMCS
* field if a VM-exit is delivered before the debug trap.
*/
static void nested_vmx_update_pending_dbg(struct kvm_vcpu *vcpu)
{
if (vmx_pending_dbg_trap(vcpu))
vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS,
vcpu->arch.exception.payload);
}
static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@ -3587,6 +3614,7 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
test_bit(KVM_APIC_INIT, &apic->pending_events)) {
if (block_nested_events)
return -EBUSY;
nested_vmx_update_pending_dbg(vcpu);
clear_bit(KVM_APIC_INIT, &apic->pending_events);
nested_vmx_vmexit(vcpu, EXIT_REASON_INIT_SIGNAL, 0, 0);
return 0;