linux-kernel - [PATCH v2 2/9] KVM: x86: fix DR6 delivery for various cases of #DB injection

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Date:   Thu,  7 May 2020 07:50:04 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     peterx@...hat.com
Subject: [PATCH v2 2/9] KVM: x86: fix DR6 delivery for various cases of #DB injection

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@...hat.com>
Reviewed-by: Peter Xu <peterx@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/vmx/vmx.c          |  8 ++------
 arch/x86/kvm/x86.c              | 11 ++++++-----
 3 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0dea9f122bb9..8c247bcb037e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1449,6 +1449,7 @@ bool kvm_rdpmc(struct kvm_vcpu *vcpu);
 
 void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr);
 void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
+void kvm_queue_exception_p(struct kvm_vcpu *vcpu, unsigned nr, unsigned long payload);
 void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr);
 void kvm_requeue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
 void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c2c6335a998c..bb5a527e49d9 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4677,12 +4677,10 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
 		dr6 = vmcs_readl(EXIT_QUALIFICATION);
 		if (!(vcpu->guest_debug &
 		      (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))) {
-			vcpu->arch.dr6 &= ~DR_TRAP_BITS;
-			vcpu->arch.dr6 |= dr6 | DR6_RTM;
 			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 +4934,7 @@ 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 d786c7d27ce5..109115c96897 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;
@@ -572,11 +574,12 @@ void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr)
 }
 EXPORT_SYMBOL_GPL(kvm_requeue_exception);
 
-static void kvm_queue_exception_p(struct kvm_vcpu *vcpu, unsigned nr,
-				  unsigned long payload)
+void kvm_queue_exception_p(struct kvm_vcpu *vcpu, unsigned nr,
+			   unsigned long payload)
 {
 	kvm_multiple_exception(vcpu, nr, false, 0, true, payload, false);
 }
+EXPORT_SYMBOL_GPL(kvm_queue_exception_p);
 
 static void kvm_queue_exception_e_p(struct kvm_vcpu *vcpu, unsigned nr,
 				    u32 error_code, unsigned long payload)
@@ -6719,9 +6722,7 @@ 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