KVM: x86: Fix guest debug across vcpu INIT reset

If we reset a vcpu on INIT, we so far overwrote dr7 as provided by
KVM_SET_GUEST_DEBUG, and we also cleared switch_db_regs unconditionally.

Fix this by saving the dr7 used for guest debugging and calculating the
effective register value as well as switch_db_regs on any potential
change. This will change to focus of the set_guest_debug vendor op to
update_dp_bp_intercept.

Found while trying to stop on start_secondary.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 4 insertions, 19 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 818fceb3091e..d017df3899ef 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1146,7 +1146,6 @@ static void init_vmcb(struct vcpu_svm *svm)
 
         svm_set_efer(&svm->vcpu, 0);
         save->dr6 = 0xffff0ff0;
-        save->dr7 = 0x400;
         kvm_set_rflags(&svm->vcpu, 2);
         save->rip = 0x0000fff0;
         svm->vcpu.arch.regs[VCPU_REGS_RIP] = save->rip;
@@ -1643,7 +1642,7 @@ static void svm_set_segment(struct kvm_vcpu *vcpu,
         mark_dirty(svm->vmcb, VMCB_SEG);
 }
 
-static void update_db_intercept(struct kvm_vcpu *vcpu)
+static void update_db_bp_intercept(struct kvm_vcpu *vcpu)
 {
         struct vcpu_svm *svm = to_svm(vcpu);
 
@@ -1663,20 +1662,6 @@ static void update_db_intercept(struct kvm_vcpu *vcpu)
                 vcpu->guest_debug = 0;
 }
 
-static void svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
-{
-        struct vcpu_svm *svm = to_svm(vcpu);
-
-        if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
-                svm->vmcb->save.dr7 = dbg->arch.debugreg[7];
-        else
-                svm->vmcb->save.dr7 = vcpu->arch.dr7;
-
-        mark_dirty(svm->vmcb, VMCB_DR);
-
-        update_db_intercept(vcpu);
-}
-
 static void new_asid(struct vcpu_svm *svm, struct svm_cpu_data *sd)
 {
         if (sd->next_asid > sd->max_asid) {
@@ -1748,7 +1733,7 @@ static int db_interception(struct vcpu_svm *svm)
                 if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP))
                         svm->vmcb->save.rflags &=
                                 ~(X86_EFLAGS_TF | X86_EFLAGS_RF);
-                update_db_intercept(&svm->vcpu);
+                update_db_bp_intercept(&svm->vcpu);
         }
 
         if (svm->vcpu.guest_debug &
@@ -3659,7 +3644,7 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
          */
         svm->nmi_singlestep = true;
         svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
-        update_db_intercept(vcpu);
+        update_db_bp_intercept(vcpu);
 }
 
 static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
@@ -4253,7 +4238,7 @@ static struct kvm_x86_ops svm_x86_ops = {
         .vcpu_load = svm_vcpu_load,
         .vcpu_put = svm_vcpu_put,
 
-        .set_guest_debug = svm_guest_debug,
+        .update_db_bp_intercept = update_db_bp_intercept,
         .get_msr = svm_get_msr,
         .set_msr = svm_set_msr,
         .get_segment_base = svm_get_segment_base,