KVM: x86: fix singlestepping over syscall

[sagit-ice-cold/kernel_xiaomi_msm8998.git] / arch / x86 / kvm / x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cba30e7..3ffd590 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4844,6 +4844,8 @@ static bool emulator_get_segment(struct x86_emulate_ctxt *ctxt, u16 *selector,
 
        if (var.unusable) {
                memset(desc, 0, sizeof(*desc));
+               if (base3)
+                       *base3 = 0;
                return false;
        }
 
@@ -4999,6 +5001,16 @@ static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
        kvm_x86_ops->set_nmi_mask(emul_to_vcpu(ctxt), masked);
 }
 
+static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
+{
+       return emul_to_vcpu(ctxt)->arch.hflags;
+}
+
+static void emulator_set_hflags(struct x86_emulate_ctxt *ctxt, unsigned emul_flags)
+{
+       kvm_set_hflags(emul_to_vcpu(ctxt), emul_flags);
+}
+
 static const struct x86_emulate_ops emulate_ops = {
        .read_gpr            = emulator_read_gpr,
        .write_gpr           = emulator_write_gpr,
@@ -5038,6 +5050,8 @@ static const struct x86_emulate_ops emulate_ops = {
        .intercept           = emulator_intercept,
        .get_cpuid           = emulator_get_cpuid,
        .set_nmi_mask        = emulator_set_nmi_mask,
+       .get_hflags          = emulator_get_hflags,
+       .set_hflags          = emulator_set_hflags,
 };
 
 static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask)
@@ -5081,6 +5095,8 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
        kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
 
        ctxt->eflags = kvm_get_rflags(vcpu);
+       ctxt->tf = (ctxt->eflags & X86_EFLAGS_TF) != 0;
+
        ctxt->eip = kvm_rip_read(vcpu);
        ctxt->mode = (!is_protmode(vcpu))               ? X86EMUL_MODE_REAL :
                     (ctxt->eflags & X86_EFLAGS_VM)     ? X86EMUL_MODE_VM86 :
@@ -5090,7 +5106,6 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
        BUILD_BUG_ON(HF_GUEST_MASK != X86EMUL_GUEST_MASK);
        BUILD_BUG_ON(HF_SMM_MASK != X86EMUL_SMM_MASK);
        BUILD_BUG_ON(HF_SMM_INSIDE_NMI_MASK != X86EMUL_SMM_INSIDE_NMI_MASK);
-       ctxt->emul_flags = vcpu->arch.hflags;
 
        init_decode_cache(ctxt);
        vcpu->arch.emulate_regs_need_sync_from_vcpu = false;
@@ -5302,37 +5317,26 @@ 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, unsigned long rflags, int *r)
+static void kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu, int *r)
 {
        struct kvm_run *kvm_run = vcpu->run;
 
-       /*
-        * rflags is the old, "raw" value of the flags.  The new value 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".
-        */
-       if (unlikely(rflags & X86_EFLAGS_TF)) {
-               if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
-                       kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 |
-                                                 DR6_RTM;
-                       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 | DR6_RTM;
-                       kvm_queue_exception(vcpu, DB_VECTOR);
-               }
+       if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+               kvm_run->debug.arch.dr6 = DR6_BS | DR6_FIXED_1 | DR6_RTM;
+               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 | DR6_RTM;
+               kvm_queue_exception(vcpu, DB_VECTOR);
        }
 }
 
@@ -5486,11 +5490,10 @@ restart:
                unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
                toggle_interruptibility(vcpu, ctxt->interruptibility);
                vcpu->arch.emulate_regs_need_sync_to_vcpu = false;
-               if (vcpu->arch.hflags != ctxt->emul_flags)
-                       kvm_set_hflags(vcpu, ctxt->emul_flags);
                kvm_rip_write(vcpu, ctxt->eip);
-               if (r == EMULATE_DONE)
-                       kvm_vcpu_check_singlestep(vcpu, rflags, &r);
+               if (r == EMULATE_DONE &&
+                   (ctxt->tf || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)))
+                       kvm_vcpu_do_singlestep(vcpu, &r);
                if (!ctxt->have_exception ||
                    exception_type(ctxt->exception.vector) == EXCPT_TRAP)
                        __kvm_set_rflags(vcpu, ctxt->eflags);