1 files changed, 38 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 89313187d7f7..05afd1ac5563 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4971,6 +4971,41 @@ static int kvm_vcpu_check_hw_bp(unsigned long addr, u32 type, u32 dr7,
         return dr6;
 }
 
+static void kvm_vcpu_check_singlestep(struct kvm_vcpu *vcpu, int *r)
+{
+        struct kvm_run *kvm_run = vcpu->run;
+
+        /*
+         * Use the "raw" value to see if TF was passed to the processor.
+         * Note that the new value of the flags has not been saved yet.
+         *
+         * This is correct even for TF set by the guest, because "the
+         * processor will not generate this exception after the instruction
+         * that sets the TF flag".
+         */
+        unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
+
+        if (unlikely(rflags & X86_EFLAGS_TF)) {
+                if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+                        kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1;
+                        kvm_run->debug.arch.pc = vcpu->arch.singlestep_rip;
+                        kvm_run->debug.arch.exception = DB_VECTOR;
+                        kvm_run->exit_reason = KVM_EXIT_DEBUG;
+                        *r = EMULATE_USER_EXIT;
+                } else {
+                        vcpu->arch.emulate_ctxt.eflags &= ~X86_EFLAGS_TF;
+                        /*
+                         * "Certain debug exceptions may clear bit 0-3.  The
+                         * remaining contents of the DR6 register are never
+                         * cleared by the processor".
+                         */
+                        vcpu->arch.dr6 &= ~15;
+                        vcpu->arch.dr6 |= DR6_BS;
+                        kvm_queue_exception(vcpu, DB_VECTOR);
+                }
+        }
+}
+
 static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
 {
         struct kvm_run *kvm_run = vcpu->run;
@@ -5117,10 +5152,12 @@ restart:
 
         if (writeback) {
                 toggle_interruptibility(vcpu, ctxt->interruptibility);
-                kvm_set_rflags(vcpu, ctxt->eflags);
                 kvm_make_request(KVM_REQ_EVENT, vcpu);
                 vcpu->arch.emulate_regs_need_sync_to_vcpu = false;
                 kvm_rip_write(vcpu, ctxt->eip);
+                if (r == EMULATE_DONE)
+                        kvm_vcpu_check_singlestep(vcpu, &r);
+                kvm_set_rflags(vcpu, ctxt->eflags);
         } else
                 vcpu->arch.emulate_regs_need_sync_to_vcpu = true;