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, 1 insertions, 13 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 30bcb953afee..5d46c905e06f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2288,16 +2288,6 @@ static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
         }
 }
 
-static void set_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
-{
-        if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
-                vmcs_writel(GUEST_DR7, dbg->arch.debugreg[7]);
-        else
-                vmcs_writel(GUEST_DR7, vcpu->arch.dr7);
-
-        update_exception_bitmap(vcpu);
-}
-
 static __init int cpu_has_kvm_support(void)
 {
         return cpu_has_vmx();
@@ -3960,8 +3950,6 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
                 kvm_rip_write(vcpu, 0);
         kvm_register_write(vcpu, VCPU_REGS_RSP, 0);
 
-        vmcs_writel(GUEST_DR7, 0x400);
-
         vmcs_writel(GUEST_GDTR_BASE, 0);
         vmcs_write32(GUEST_GDTR_LIMIT, 0xffff);
 
@@ -7237,7 +7225,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
         .vcpu_load = vmx_vcpu_load,
         .vcpu_put = vmx_vcpu_put,
 
-        .set_guest_debug = set_guest_debug,
+        .update_db_bp_intercept = update_exception_bitmap,
         .get_msr = vmx_get_msr,
         .set_msr = vmx_set_msr,
         .get_segment_base = vmx_get_segment_base,