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KVM: x86: handle hardware breakpoints during emulation

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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>
This commit is contained in:
Paolo Bonzini 2013-05-30 11:48:30 +02:00
parent ac0a48c39a
commit 4a1e10d5b5
1 changed files with 66 additions and 0 deletions
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66
arch/x86/kvm/x86.c
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@ -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;