KVM: x86: handle hardware breakpoints during emulation
authorPaolo Bonzini <pbonzini@redhat.com>
Thu, 30 May 2013 09:48:30 +0000 (11:48 +0200)
committerPaolo Bonzini <pbonzini@redhat.com>
Mon, 29 Jul 2013 07:01:14 +0000 (09:01 +0200)
This lets debugging work better during emulation of invalid
guest state.

The check is done before emulating the instruction, and (in the case
of guest debugging) reuses EMULATE_DO_MMIO to exit with KVM_EXIT_DEBUG.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
arch/x86/kvm/x86.c

index 8589cc02789ecffb9624185a9f6b583d6e25f023..89313187d7f7dd057a0fb5ecb60931ed0e2da54e 100644 (file)
@@ -4956,6 +4956,62 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
 static int complete_emulated_mmio(struct kvm_vcpu *vcpu);
 static int complete_emulated_pio(struct kvm_vcpu *vcpu);
 
+static int kvm_vcpu_check_hw_bp(unsigned long addr, u32 type, u32 dr7,
+                               unsigned long *db)
+{
+       u32 dr6 = 0;
+       int i;
+       u32 enable, rwlen;
+
+       enable = dr7;
+       rwlen = dr7 >> 16;
+       for (i = 0; i < 4; i++, enable >>= 2, rwlen >>= 4)
+               if ((enable & 3) && (rwlen & 15) == type && db[i] == addr)
+                       dr6 |= (1 << i);
+       return dr6;
+}
+
+static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
+{
+       struct kvm_run *kvm_run = vcpu->run;
+       unsigned long eip = vcpu->arch.emulate_ctxt.eip;
+       u32 dr6 = 0;
+
+       if (unlikely(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) &&
+           (vcpu->arch.guest_debug_dr7 & DR7_BP_EN_MASK)) {
+               dr6 = kvm_vcpu_check_hw_bp(eip, 0,
+                                          vcpu->arch.guest_debug_dr7,
+                                          vcpu->arch.eff_db);
+
+               if (dr6 != 0) {
+                       kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1;
+                       kvm_run->debug.arch.pc = kvm_rip_read(vcpu) +
+                               get_segment_base(vcpu, VCPU_SREG_CS);
+
+                       kvm_run->debug.arch.exception = DB_VECTOR;
+                       kvm_run->exit_reason = KVM_EXIT_DEBUG;
+                       *r = EMULATE_USER_EXIT;
+                       return true;
+               }
+       }
+
+       if (unlikely(vcpu->arch.dr7 & DR7_BP_EN_MASK)) {
+               dr6 = kvm_vcpu_check_hw_bp(eip, 0,
+                                          vcpu->arch.dr7,
+                                          vcpu->arch.db);
+
+               if (dr6 != 0) {
+                       vcpu->arch.dr6 &= ~15;
+                       vcpu->arch.dr6 |= dr6;
+                       kvm_queue_exception(vcpu, DB_VECTOR);
+                       *r = EMULATE_DONE;
+                       return true;
+               }
+       }
+
+       return false;
+}
+
 int x86_emulate_instruction(struct kvm_vcpu *vcpu,
                            unsigned long cr2,
                            int emulation_type,
@@ -4976,6 +5032,16 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
 
        if (!(emulation_type & EMULTYPE_NO_DECODE)) {
                init_emulate_ctxt(vcpu);
+
+               /*
+                * We will reenter on the same instruction since
+                * we do not set complete_userspace_io.  This does not
+                * handle watchpoints yet, those would be handled in
+                * the emulate_ops.
+                */
+               if (kvm_vcpu_check_breakpoint(vcpu, &r))
+                       return r;
+
                ctxt->interruptibility = 0;
                ctxt->have_exception = false;
                ctxt->perm_ok = false;