Gleb Natapov wrote: > On Mon, Feb 15, 2010 at 07:17:17PM +0100, Jan Kiszka wrote: >> When in guest debugging mode, we have to reinject those #BP software >> exceptions that are caused by guest-injected INT3. As older AMD >> processors to not support the required nRIP VMCB field, try to emulate >> it by moving RIP by one on injection. Fix it up again in case the >> injection failed and we were able to catch this. This does not work for >> unintercepted faults, but it is better than doing nothing. >> >> Signed-off-by: Jan Kiszka <[email protected]> >> --- >> arch/x86/kvm/svm.c | 54 >> +++++++++++++++++++++++++++++++++++---------------- >> 1 files changed, 37 insertions(+), 17 deletions(-) >> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index 52f78dd..f63f1db 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -46,6 +46,7 @@ MODULE_LICENSE("GPL"); >> #define SVM_FEATURE_NPT (1 << 0) >> #define SVM_FEATURE_LBRV (1 << 1) >> #define SVM_FEATURE_SVML (1 << 2) >> +#define SVM_FEATURE_NRIP (1 << 3) >> #define SVM_FEATURE_PAUSE_FILTER (1 << 10) >> >> #define NESTED_EXIT_HOST 0 /* Exit handled on host level */ >> @@ -109,6 +110,8 @@ struct vcpu_svm { >> struct nested_state nested; >> >> bool nmi_singlestep; >> + >> + bool int3_injected; >> }; >> >> /* enable NPT for AMD64 and X86 with PAE */ >> @@ -234,23 +237,6 @@ static void svm_set_efer(struct kvm_vcpu *vcpu, u64 >> efer) >> vcpu->arch.efer = efer; >> } >> >> -static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr, >> - bool has_error_code, u32 error_code) >> -{ >> - struct vcpu_svm *svm = to_svm(vcpu); >> - >> - /* If we are within a nested VM we'd better #VMEXIT and let the >> - guest handle the exception */ >> - if (nested_svm_check_exception(svm, nr, has_error_code, error_code)) >> - return; >> - >> - svm->vmcb->control.event_inj = nr >> - | SVM_EVTINJ_VALID >> - | (has_error_code ? SVM_EVTINJ_VALID_ERR : 0) >> - | SVM_EVTINJ_TYPE_EXEPT; >> - svm->vmcb->control.event_inj_err = error_code; >> -} >> - >> static int is_external_interrupt(u32 info) >> { >> info &= SVM_EVTINJ_TYPE_MASK | SVM_EVTINJ_VALID; >> @@ -296,6 +282,36 @@ static void skip_emulated_instruction(struct kvm_vcpu >> *vcpu) >> svm_set_interrupt_shadow(vcpu, 0); >> } >> >> +static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr, >> + bool has_error_code, u32 error_code) >> +{ >> + struct vcpu_svm *svm = to_svm(vcpu); >> + >> + /* If we are within a nested VM we'd better #VMEXIT and let the >> + guest handle the exception */ >> + if (nested_svm_check_exception(svm, nr, has_error_code, error_code)) >> + return; >> + >> + if (nr == BP_VECTOR && !svm_has(SVM_FEATURE_NRIP)) { >> + /* >> + * For guest debugging where we have to reinject #BP if some >> + * INT3 is guest-owned: >> + * Emulate nRIP by moving RIP one forward. Will fail if >> + * injection raises a fault that is not intercepted. Still >> + * better than failing in all cases. >> + */ >> + svm->next_rip = kvm_rip_read(&svm->vcpu) + 1; >> + skip_emulated_instruction(&svm->vcpu); > if next_rip is zero skip_emulated_instruction() decodes instruction by > itself to properly calculate next rip so no need to guess instruction > length.
Just copied what all the instruction emulations do here. Can change, though.
>
>> + svm->int3_injected = true;
>> + }
>> +
>> + svm->vmcb->control.event_inj = nr
>> + | SVM_EVTINJ_VALID
>> + | (has_error_code ? SVM_EVTINJ_VALID_ERR : 0)
>> + | SVM_EVTINJ_TYPE_EXEPT;
>> + svm->vmcb->control.event_inj_err = error_code;
>> +}
>> +
>> static int has_svm(void)
>> {
>> const char *msg;
>> @@ -2653,6 +2669,9 @@ static void svm_complete_interrupts(struct vcpu_svm
>> *svm)
>> if (is_nested(svm))
>> break;
>> if (kvm_exception_is_soft(vector))
>> + if (vector == BP_VECTOR && svm->int3_injected)
>> + kvm_rip_write(&svm->vcpu,
>> + kvm_rip_read(&svm->vcpu) - 1);
> You don't even check current rip? So if fault happens during unrelated #BP
> you move
> rip backwards and restart.
Yep, true. Will fix.
>
>> break;
>> if (exitintinfo & SVM_EXITINTINFO_VALID_ERR) {
>> u32 err = svm->vmcb->control.exit_int_info_err;
>> @@ -2667,6 +2686,7 @@ static void svm_complete_interrupts(struct vcpu_svm
>> *svm)
>> default:
>> break;
>> }
>> + svm->int3_injected =false;
> Looks like the wrong place to clear this. It should be cleared on every
> exit, not only with valid vectoring info.
Right.
>
>> }
>>
>> #ifdef CONFIG_X86_64
>> --
>> 1.6.0.2
>
> --
> Gleb.
Thanks,
Jan
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