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[03/12] KVM: VMX: Fix DR6 update on #DB exception

Message ID b3f12dbcd55e805595b668da8996ab307b090e23.1388857646.git.jan.kiszka@web.de (mailing list archive)
State New, archived
Headers show

Commit Message

Jan Kiszka Jan. 4, 2014, 5:47 p.m. UTC 
From: Jan Kiszka <jan.kiszka@siemens.com>

According to the SDM, only bits 0-3 of DR6 "may" be cleared by "certain"
debug exception. So do update them on #DB exception in KVM, but leave
the rest alone, only setting BD and BS in addition to already set bits
in DR6. This also aligns us with kvm_vcpu_check_singlestep.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 arch/x86/kvm/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
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Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 55cb4b6..2a95ce0 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4869,7 +4869,8 @@  static int handle_exception(struct kvm_vcpu *vcpu)
 		dr6 = vmcs_readl(EXIT_QUALIFICATION);
 		if (!(vcpu->guest_debug &
 		      (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))) {
-			vcpu->arch.dr6 = dr6 | DR6_FIXED_1;
+			vcpu->arch.dr6 &= ~15;
+			vcpu->arch.dr6 |= dr6;
 			kvm_queue_exception(vcpu, DB_VECTOR);
 			return 1;
 		}