On Thu, May 30, 2013 at 06:00:30PM +0200, Paolo Bonzini wrote:
> 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 */
If it no longer means MMIO (or PIO) lest rename it to something more
meaningful. EMULATE_EXIT? EMULATE_USER_EXIT?
> EMULATE_FAIL, /* can't emulate this instruction */
> + EMULATE_PROCEED, /* proceed with rest of emulation */
I think we can do without this. Have to function: check_bp(),
handle_bp(). Do:
if (check_bp())
return handle_bp();
> };
>
> #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
>
--
Gleb.
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