KVM: X86: Rename DR6_INIT to DR6_ACTIVE_LOW
DR6_INIT contains the 1-reserved bits as well as the bit that is cleared
to 0 when the condition (e.g. RTM) happens. The value can be used to
initialize dr6 and also be the XOR mask between the #DB exit
qualification (or payload) and DR6.
Concerning that DR6_INIT is used as initial value only once, rename it
to DR6_ACTIVE_LOW and apply it in other places, which would make the
incoming changes for bus lock debug exception more simple.
Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-2-chenyi.qiang@intel.com>
[Define DR6_FIXED_1 from DR6_ACTIVE_LOW and DR6_VOLATILE. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0ecbb4e..fae4ccb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -486,19 +486,24 @@ void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu)
*/
vcpu->arch.dr6 &= ~DR_TRAP_BITS;
/*
- * DR6.RTM is set by all #DB exceptions that don't clear it.
+ * In order to reflect the #DB exception payload in guest
+ * dr6, three components need to be considered: active low
+ * bit, FIXED_1 bits and active high bits (e.g. DR6_BD,
+ * DR6_BS and DR6_BT)
+ * DR6_ACTIVE_LOW contains the FIXED_1 and active low bits.
+ * In the target guest dr6:
+ * FIXED_1 bits should always be set.
+ * Active low bits should be cleared if 1-setting in payload.
+ * Active high bits should be set if 1-setting in payload.
+ *
+ * Note, the payload is compatible with the pending debug
+ * exceptions/exit qualification under VMX, that active_low bits
+ * are active high in payload.
+ * So they need to be flipped for DR6.
*/
- vcpu->arch.dr6 |= DR6_RTM;
+ vcpu->arch.dr6 |= DR6_ACTIVE_LOW;
vcpu->arch.dr6 |= payload;
- /*
- * Bit 16 should be set in the payload whenever the #DB
- * exception should clear DR6.RTM. This makes the payload
- * compatible with the pending debug exceptions under VMX.
- * Though not currently documented in the SDM, this also
- * makes the payload compatible with the exit qualification
- * for #DB exceptions under VMX.
- */
- vcpu->arch.dr6 ^= payload & DR6_RTM;
+ vcpu->arch.dr6 ^= payload & DR6_ACTIVE_LOW;
/*
* The #DB payload is defined as compatible with the 'pending
@@ -7211,7 +7216,7 @@ static int kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu)
struct kvm_run *kvm_run = vcpu->run;
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
- kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | DR6_RTM;
+ kvm_run->debug.arch.dr6 = DR6_BS | DR6_ACTIVE_LOW;
kvm_run->debug.arch.pc = kvm_get_linear_rip(vcpu);
kvm_run->debug.arch.exception = DB_VECTOR;
kvm_run->exit_reason = KVM_EXIT_DEBUG;
@@ -7255,7 +7260,7 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
vcpu->arch.eff_db);
if (dr6 != 0) {
- kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM;
+ kvm_run->debug.arch.dr6 = dr6 | DR6_ACTIVE_LOW;
kvm_run->debug.arch.pc = eip;
kvm_run->debug.arch.exception = DB_VECTOR;
kvm_run->exit_reason = KVM_EXIT_DEBUG;
@@ -10118,7 +10123,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
memset(vcpu->arch.db, 0, sizeof(vcpu->arch.db));
kvm_update_dr0123(vcpu);
- vcpu->arch.dr6 = DR6_INIT;
+ vcpu->arch.dr6 = DR6_ACTIVE_LOW;
vcpu->arch.dr7 = DR7_FIXED_1;
kvm_update_dr7(vcpu);