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@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 3 +-
arch/x86/kvm/x86.c | 65 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 67 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e2e09f3..aefd8c2 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -788,9 +788,10 @@ extern u32 kvm_min_guest_tsc_khz;
extern u32 kvm_max_guest_tsc_khz;
enum emulation_result {
- EMULATE_DONE, /* no further processing */
- EMULATE_DO_MMIO, /* kvm_run filled with mmio request */
+ EMULATE_DONE, /* no further processing */
+ EMULATE_DO_MMIO, /* kvm_run ready for userspace exit */
EMULATE_FAIL, /* can't emulate this instruction */
+ EMULATE_PROCEED, /* proceed with rest of emulation */
};
#define EMULTYPE_NO_DECODE (1 << 0)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1d928af..33b51bc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4872,6 +4872,60 @@ 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 int kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu)
+{
+ 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;
+ return EMULATE_DO_MMIO;
+ }
+ }
+
+ 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);
+ return EMULATE_DONE;
+ }
+ }
+
+ return EMULATE_PROCEED;
+}
+
int x86_emulate_instruction(struct kvm_vcpu *vcpu,
unsigned long cr2,
int emulation_type,
@@ -4892,6 +4946,17 @@ 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.
+ */
+ r = kvm_vcpu_check_breakpoint(vcpu);
+ if (r != EMULATE_PROCEED)
+ return r;
+
ctxt->interruptibility = 0;
ctxt->have_exception = false;
ctxt->perm_ok = false;
--
1.8.1.4
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