Re: [Xen-devel] Last Branch Record (LBR) in Xen

[Abhinav Srivastava <abhinavs_iitkgp@xxxxxxxxxxx>]

Hi Jan,

I got it now. Thanks for the clarification. However, could you please
give me some pointers or suggestions to code this thing in the hypervisor?

Thanks,
Abhinav

--- On Fri, 26/6/09, Jan Beulich <JBeulich@xxxxxxxxxx> wrote:

> From: Jan Beulich <JBeulich@xxxxxxxxxx>
> Subject: Re: [Xen-devel] Last Branch Record (LBR) in Xen
> To: "Abhinav Srivastava" <abhinavs_iitkgp@xxxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Date: Friday, 26 June, 2009, 7:31 PM
> >>> Abhinav Srivastava
> <abhinavs_iitkgp@xxxxxxxxxxx>
> 26.06.09 15:50 >>>
> >As far as I understand (please correct me if I am
> wrong), you meant that HVM guests have to enable the LBR
> recording, and
> >this action cannot be initiated/controlled by Xen. I
> was thinking like other kind of actions, such as single
> stepping on instruction,
> >single stepping on branch etc. that can be controlled
> from the hypervisor and guests behave accordingly, the LBR
> feature can
> >also be set/reset from the hypervisor. And, if that is
> not the case then I think any malicious programs can turn
> off this feature
> >inside HVM guests and can bypass the debugger.
> Moreover, I assumed anything that a guest can do, can also
> be done from
> >the hypervisor by setting guest MSR registers or bitmap
> from the hypervisor.
> 
> Oh, of course this can be done from the hypervisor, but
> that wasn't the purpose of the patch. You'd have to code
> this for yourself.
> 
> Jan
> 
> 
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