On 1/12/21 8:01 AM, Paolo Bonzini wrote:
> On 12/01/21 07:37, Wei Huang wrote:
>> static int gp_interception(struct vcpu_svm *svm)
>> {
>> struct kvm_vcpu *vcpu = &svm->vcpu;
>> u32 error_code = svm->vmcb->control.exit_info_1;
>> -
>> - WARN_ON_ONCE(!enable_vmware_backdoor);
>> + int rc;
>> /*
>> - * VMware backdoor emulation on #GP interception only handles IN{S},
>> - * OUT{S}, and RDPMC, none of which generate a non-zero error code.
>> + * Only VMware backdoor and SVM VME errata are handled. Neither of
>> + * them has non-zero error codes.
>> */
>> if (error_code) {
>> kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
>> return 1;
>> }
>> - return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP);
>> +
>> + rc = kvm_emulate_instruction(vcpu, EMULTYPE_PARAVIRT_GP);
>> + if (rc > 1)
>> + rc = svm_emulate_vm_instr(vcpu, rc);
>> + return rc;
>> }
>>
>
> Passing back the third byte is quick hacky. Instead of this change to
> kvm_emulate_instruction, I'd rather check the instruction bytes in
> gp_interception before calling kvm_emulate_instruction. That would be
> something like:
>
> - move "kvm_clear_exception_queue(vcpu);" inside the "if
> (!(emulation_type & EMULTYPE_NO_DECODE))". It doesn't apply when you
> are coming back from userspace.
>
> - extract the "if (!(emulation_type & EMULTYPE_NO_DECODE))" body to a
> new function x86_emulate_decoded_instruction. Call it from
> gp_interception, we know this is not a pagefault and therefore
> vcpu->arch.write_fault_to_shadow_pgtable must be false.
If the whole body inside if-statement is moved out, do you expect the
interface of x86_emulate_decoded_instruction to be something like:
int x86_emulate_decoded_instruction(struct kvm_vcpu *vcpu,
gpa_t cr2_or_gpa,
int emulation_type, void *insn,
int insn_len,
bool write_fault_to_spt)
And if so, what is the emulation type to use when calling this function
from svm.c? EMULTYPE_VMWARE_GP?
>
> - check ctxt->insn_bytes for an SVM instruction
>
> - if not an SVM instruction, call kvm_emulate_instruction(vcpu,
> EMULTYPE_VMWARE_GP|EMULTYPE_NO_DECODE).
>
> Thanks,
>
> Paolo
>
