Re: [PATCH 6/6] perf intel-pt: Add guest_code support

Adrian Hunter
2022-05-13T15:15:12Z

On 13/05/22 17:46, Andi Kleen wrote:
> Adrian Hunter <adrian.hunter@intel.com> writes:
>
>> A common case for KVM test programs is that the guest object code can be
>> found in the hypervisor process (i.e. the test program running on the
>> host). To support that, a new option "--guest-code" has been added in
>> previous patches.
>>
>> In this patch, add support also to Intel PT.
>>
>> In particular, ensure guest_code thread is set up before attempting to
>> walk object code or synthesize samples.
>
> Can you make it clear in the documentation what parts runs on the host
> and what parts on the guest?

That is up to the test program. All the host thread maps are
copied, so perf tools doesn't have to know.

>
> I'm still not fully sure how it exactly finds the code on the host,
> how is the code transferred?

I don't know. From a quick look at the code in
tools/testing/selftests/kvm/lib/kvm_util.c it seems to be using
KVM_SET_USER_MEMORY_REGION IOCTL.

>
> Other than that more support for this use case is very useful.
>
> -Andi