Re: [Xen-devel] [PATCH RESEND v1 1/7] x86: add a flag to enable Intel processor trace

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.04.18 at 10:22, <luwei.kang@xxxxxxxxx> wrote:
>> > diff --git a/docs/misc/xen-command-line.markdown
>> > b/docs/misc/xen-command-line.markdown
>> > index 781110d..95411cf 100644
>> > --- a/docs/misc/xen-command-line.markdown
>> > +++ b/docs/misc/xen-command-line.markdown
>> > @@ -1009,6 +1009,13 @@ debug hypervisor only).
>> >  ### idle\_latency\_factor
>> >  > `= <integer>`
>> >
>> > +### intel\_pt
>> > +> `= <boolean>`
>> > +
>> > +> Default: `true`
>> > +
>> 
>> After reading the manual a bit I think this option needs to be more
>> sophisticated.
>> 
>> The series only implements guest-only tracing, while in the future we might
>> want host-only tracing and system wide tracing.
>> 
>> Even the other modes aren't implemented yet we should leave room for
>> them.
>> 
> 
> Hi Wei,
>      Thanks for the review. So what about define guest mode like this and 
> make the option as a string. Other mode can be added like 'system | host' in 
> future.
> 
> ### Intel\_pt
>> `= guest`

That's still too simple, as you implement it for HVM only. While it's not clear
to me whether it could be done properly for PV, that path shouldn't be closed
unless it's crystal clear that it's impossible to ever happen.

Jan



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