Re: [Xen-devel] [SVM] Getting the length of the current instruction in svm_vmexit_handler()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.03.18 at 15:56, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> We'd like to retrieve the length of the current instruction in
> svm_vmexit_handler(), specifically for the VMEXIT_EXCEPTION_DB and
> VMEXIT_EXCEPTION_BP cases.
> 
> We've combed the vmcb to no avail. Everything we've thought to check
> (exitinfo1, exitinfo2, exitintinfo) turns out to be zero there while
> testing.
> 
> There's __get_instruction_length(vcpu, instr), but it expects to be fed
> the exact instruction we want the length for, which obviously defeats
> the purpose here.
> 
> Is there a clean way to get the current instruction length like we do in
> the VMX case (__vmread(VM_EXIT_INSTRUCTION_LEN, &insn_len)) that we're
> overlooking?

Just like Intel's, AMD's is available in a subset of cases only
(look for vmcb->guest_ins_len), which don't include the
exception intercepts you talk about. For #DB I think there's
no difference between both anyway.

Jan


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