2 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 35f538bda3a9..fcaf9c961265 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -339,6 +339,7 @@ struct kvm_pmu {
 
 enum {
         KVM_DEBUGREG_BP_ENABLED = 1,
+        KVM_DEBUGREG_WONT_EXIT = 2,
 };
 
 struct kvm_vcpu_arch {
@@ -707,6 +708,7 @@ struct kvm_x86_ops {
         void (*set_gdt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt);
         u64 (*get_dr6)(struct kvm_vcpu *vcpu);
         void (*set_dr6)(struct kvm_vcpu *vcpu, unsigned long value);
+        void (*sync_dirty_debug_regs)(struct kvm_vcpu *vcpu);
         void (*set_dr7)(struct kvm_vcpu *vcpu, unsigned long value);
         void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
         unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 85c74e7df2df..d906391a0a3f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6040,12 +6040,28 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                 set_debugreg(vcpu->arch.eff_db[1], 1);
                 set_debugreg(vcpu->arch.eff_db[2], 2);
                 set_debugreg(vcpu->arch.eff_db[3], 3);
+                set_debugreg(vcpu->arch.dr6, 6);
         }
 
         trace_kvm_entry(vcpu->vcpu_id);
         kvm_x86_ops->run(vcpu);
 
         /*
+         * Do this here before restoring debug registers on the host.  And
+         * since we do this before handling the vmexit, a DR access vmexit
+         * can (a) read the correct value of the debug registers, (b) set
+         * KVM_DEBUGREG_WONT_EXIT again.
+         */
+        if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT)) {
+                int i;
+
+                WARN_ON(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP);
+                kvm_x86_ops->sync_dirty_debug_regs(vcpu);
+                for (i = 0; i < KVM_NR_DB_REGS; i++)
+                        vcpu->arch.eff_db[i] = vcpu->arch.db[i];
+        }
+
+        /*
          * If the guest has used debug registers, at least dr7
          * will be disabled while returning to the host.
          * If we don't have active breakpoints in the host, we don't