[PATCH v2] KVM: x86: fix DR6 delivery for various cases of #DB injection

From: Paolo Bonzini
Date: Wed May 06 2020 - 05:22:33 EST


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.

Reported-by: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 6 ++----
arch/x86/kvm/x86.c | 6 +++---
2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c2c6335a998c..254c46a5d69d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4682,7 +4682,7 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
if (is_icebp(intr_info))
WARN_ON(!skip_emulated_instruction(vcpu));

- kvm_queue_exception(vcpu, DB_VECTOR);
+ kvm_queue_exception_p(vcpu, DB_VECTOR, dr6);
return 1;
}
kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1;
@@ -4936,9 +4936,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
vcpu->run->exit_reason = KVM_EXIT_DEBUG;
return 0;
} else {
- vcpu->arch.dr6 &= ~DR_TRAP_BITS;
- vcpu->arch.dr6 |= DR6_BD | DR6_RTM;
- kvm_queue_exception(vcpu, DB_VECTOR);
+ kvm_queue_exception_p(vcpu, DB_VECTOR, DR6_BD);
return 1;
}
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c5835f9cb9ad..f571e40de438 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -104,6 +104,7 @@ static u64 __read_mostly cr4_reserved_bits = CR4_RESERVED_BITS;
KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)

static void update_cr8_intercept(struct kvm_vcpu *vcpu);
+static void kvm_update_dr6(struct kvm_vcpu *vcpu);
static void process_nmi(struct kvm_vcpu *vcpu);
static void enter_smm(struct kvm_vcpu *vcpu);
static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags);
@@ -473,6 +474,7 @@ 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 +6733,7 @@ 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