[PATCH 1/7] KVM: x86: Set guest DR6 by kvm_queue_exception_p() in instruction emulation

[Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>]

Record DR6 in emulate_db() and use kvm_queue_exception_p() to set DR6
instead of directly using kvm_set_dr6() in emulation, which keeps the
handling of DR6 during #DB injection consistent with other code paths.

No functional change intended.

Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
---
 arch/x86/kvm/emulate.c     | 14 ++++----------
 arch/x86/kvm/kvm_emulate.h |  6 +++++-
 arch/x86/kvm/x86.c         |  3 +++
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 542d3664afa3..18e3a732d106 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -593,8 +593,9 @@ static int emulate_exception(struct x86_emulate_ctxt *ctxt, int vec,
 	return X86EMUL_PROPAGATE_FAULT;
 }
 
-static int emulate_db(struct x86_emulate_ctxt *ctxt)
+static int emulate_db(struct x86_emulate_ctxt *ctxt, unsigned long dr6)
 {
+	ctxt->exception.dr6 = dr6;
 	return emulate_exception(ctxt, DB_VECTOR, 0, false);
 }
 
@@ -3857,15 +3858,8 @@ static int check_dr_read(struct x86_emulate_ctxt *ctxt)
 	if ((cr4 & X86_CR4_DE) && (dr == 4 || dr == 5))
 		return emulate_ud(ctxt);
 
-	if (ctxt->ops->get_dr(ctxt, 7) & DR7_GD) {
-		ulong dr6;
-
-		dr6 = ctxt->ops->get_dr(ctxt, 6);
-		dr6 &= ~DR_TRAP_BITS;
-		dr6 |= DR6_BD | DR6_ACTIVE_LOW;
-		ctxt->ops->set_dr(ctxt, 6, dr6);
-		return emulate_db(ctxt);
-	}
+	if (ctxt->ops->get_dr(ctxt, 7) & DR7_GD)
+		return emulate_db(ctxt, DR6_BD);
 
 	return X86EMUL_CONTINUE;
 }
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 7b5ddb787a25..a6fad7b938e3 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -24,7 +24,11 @@ struct x86_exception {
 	bool error_code_valid;
 	u16 error_code;
 	bool nested_page_fault;
-	u64 address; /* cr2 or nested page fault gpa */
+	union {
+		u64 address; /* cr2 or nested page fault gpa */
+		unsigned long dr6;
+		u64 payload;
+	};
 	u8 async_page_fault;
 	unsigned long exit_qualification;
 };
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7ba2cdfdac44..b2e8322aeca7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8612,6 +8612,8 @@ static void inject_emulated_exception(struct kvm_vcpu *vcpu)
 
 	if (ctxt->exception.vector == PF_VECTOR)
 		kvm_inject_emulated_page_fault(vcpu, &ctxt->exception);
+	else if (ctxt->exception.vector == DB_VECTOR)
+		kvm_queue_exception_p(vcpu, DB_VECTOR, ctxt->exception.dr6);
 	else if (ctxt->exception.error_code_valid)
 		kvm_queue_exception_e(vcpu, ctxt->exception.vector,
 				      ctxt->exception.error_code);
@@ -8656,6 +8658,7 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
 	ctxt->interruptibility = 0;
 	ctxt->have_exception = false;
 	ctxt->exception.vector = -1;
+	ctxt->exception.payload = 0;
 	ctxt->perm_ok = false;
 
 	init_decode_cache(ctxt);
-- 
2.31.1