[PATCH] KVM: x86: fix DR6 delivery for emulated hardware breakpoint

[PATCH] KVM: x86: fix DR6 delivery for emulated hardware breakpoint

[Paolo Bonzini]

Go through kvm_queue_exception_p so that the payload is correctly delivered
through the exit qualification, and add a kvm_update_dr6 call to
kvm_deliver_exception_payload that is needed on AMD.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/x86.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c5835f9cb9ad..8f61cb15f147 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -473,6 +473,7 @@ void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu)
 		 * breakpoint), it is reserved and must be zero in DR6.
 		 */
 		vcpu->arch.dr6 &= ~BIT(12);
+		kvm_update_dr6(vcpu);
 		break;
 	case PF_VECTOR:
 		vcpu->arch.cr2 = payload;
@@ -6731,9 +6732,7 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
 					   vcpu->arch.db);
 
 		if (dr6 != 0) {
-			vcpu->arch.dr6 &= ~DR_TRAP_BITS;
-			vcpu->arch.dr6 |= dr6 | DR6_RTM;
-			kvm_queue_exception(vcpu, DB_VECTOR);
+			kvm_queue_exception_p(vcpu, DB_VECTOR, dr6);
 			*r = 1;
 			return true;
 		}
-- 
2.18.2

Re: [PATCH] KVM: x86: fix DR6 delivery for emulated hardware breakpoint

[Peter Xu]

On Tue, May 05, 2020 at 07:34:49AM -0400, Paolo Bonzini wrote:
> Go through kvm_queue_exception_p so that the payload is correctly delivered
> through the exit qualification, and add a kvm_update_dr6 call to
> kvm_deliver_exception_payload that is needed on AMD.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

I still think we could also change this in handle_exception_nmi() and
handle_dr() as mentioned in the other thread, but no strong opinion:

Reviewed-by: Peter Xu <peterx@redhat.com>

Thanks,

-- 
Peter Xu