From 307f1cfa269657c63cfe2c932386fcc24684d9dd Mon Sep 17 00:00:00 2001 From: Oliver Upton Date: Fri, 7 Feb 2020 02:36:04 -0800 Subject: [PATCH] KVM: x86: Mask off reserved bit from #DB exception payload KVM defines the #DB payload as compatible with the 'pending debug exceptions' field under VMX, not DR6. Mask off bit 12 when applying the payload to DR6, as it is reserved on DR6 but not the 'pending debug exceptions' field. Fixes: f10c729ff965 ("kvm: vmx: Defer setting of DR6 until #DB delivery") Signed-off-by: Oliver Upton Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index fbabb2f06273b..95b753dab2079 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -438,6 +438,14 @@ void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu) * for #DB exceptions under VMX. */ vcpu->arch.dr6 ^= payload & DR6_RTM; + + /* + * The #DB payload is defined as compatible with the 'pending + * debug exceptions' field under VMX, not DR6. While bit 12 is + * defined in the 'pending debug exceptions' field (enabled + * breakpoint), it is reserved and must be zero in DR6. + */ + vcpu->arch.dr6 &= ~BIT(12); break; case PF_VECTOR: vcpu->arch.cr2 = payload; -- 2.30.2