Processor to run Intel PT in a Guest VM

Processor to run Intel PT in a Guest VM

[Aditya Basu]

Hi all,
I am a PhD student at the Pennsylvania State University. For my
current project, I am trying to run Intel Processor Trace (PT) inside
a Guest VM. Specifically, I want to run KVM in the "Host-Guest mode"
as stated in the following bug:
https://bugzilla.kernel.org/show_bug.cgi?id=201565

However, I *cannot* find an Intel processor that supports this mode. I
have tried using Intel's i7-7700 and i7-9700k processors. Based on my
findings, the problem seems to be that bit 24 (PT_USE_GPA) of
MSR_IA32_VMX_PROCBASED_CTLS2 (high) is reported as 0 by the processor.
Hence, KVM seems to force pt_mode to 0 (or PT_MODE_HOST).

I would appreciate any pointers that someone might have regarding the
above. Specifically, I want to find an Intel processor that supports
running Intel PT in "Host-Guest mode".

Regards,

Aditya Basu
PhD Student in CSE
Pennsylvania State University
https://www.adityabasu.me/

Re: Processor to run Intel PT in a Guest VM

[Xu, Like]

On 2021/3/2 2:48, Aditya Basu wrote:
> Hi all,
> I am a PhD student at the Pennsylvania State University. For my
> current project, I am trying to run Intel Processor Trace (PT) inside
> a Guest VM. Specifically, I want to run KVM in the "Host-Guest mode"
> as stated in the following bug:
> https://bugzilla.kernel.org/show_bug.cgi?id=201565
>
> However, I *cannot* find an Intel processor that supports this mode. I
> have tried using Intel's i7-7700 and i7-9700k processors. Based on my
> findings, the problem seems to be that bit 24 (PT_USE_GPA) of
> MSR_IA32_VMX_PROCBASED_CTLS2 (high) is reported as 0 by the processor.
> Hence, KVM seems to force pt_mode to 0 (or PT_MODE_HOST).

You may try the Intel Atom® Processor P* Series.

https://ark.intel.com/content/www/us/en/ark/products/series/29035/intel-atom-processor.html?wapkw=Atom#@Server

>
> I would appreciate any pointers that someone might have regarding the
> above. Specifically, I want to find an Intel processor that supports
> running Intel PT in "Host-Guest mode".
>
> Regards,
>
> Aditya Basu
> PhD Student in CSE
> Pennsylvania State University
> https://www.adityabasu.me/

Re: Processor to run Intel PT in a Guest VM

[Aditya Basu]

Thanks a lot for the information. From what I see, the Atom P series
are server-grade processors.

Would you happen to know if any Desktop/Workstation processors (ex.
10th gen i9) also support this feature?
Specifically, I'm referring to Comet Lake, here --

https://ark.intel.com/content/www/us/en/ark/products/codename/90354/comet-lake.html

Aditya


Aditya

On Mon, Mar 1, 2021 at 8:16 PM Xu, Like <like.xu@intel.com> wrote:
>
> On 2021/3/2 2:48, Aditya Basu wrote:
> > Hi all,
> > I am a PhD student at the Pennsylvania State University. For my
> > current project, I am trying to run Intel Processor Trace (PT) inside
> > a Guest VM. Specifically, I want to run KVM in the "Host-Guest mode"
> > as stated in the following bug:
> > https://bugzilla.kernel.org/show_bug.cgi?id=201565
> >
> > However, I *cannot* find an Intel processor that supports this mode. I
> > have tried using Intel's i7-7700 and i7-9700k processors. Based on my
> > findings, the problem seems to be that bit 24 (PT_USE_GPA) of
> > MSR_IA32_VMX_PROCBASED_CTLS2 (high) is reported as 0 by the processor.
> > Hence, KVM seems to force pt_mode to 0 (or PT_MODE_HOST).
>
> You may try the Intel Atom® Processor P* Series.
>
> https://ark.intel.com/content/www/us/en/ark/products/series/29035/intel-atom-processor.html?wapkw=Atom#@Server
>
> >
> > I would appreciate any pointers that someone might have regarding the
> > above. Specifically, I want to find an Intel processor that supports
> > running Intel PT in "Host-Guest mode".
> >
> > Regards,
> >
> > Aditya Basu
> > PhD Student in CSE
> > Pennsylvania State University
> > https://www.adityabasu.me/
>

Re: Processor to run Intel PT in a Guest VM

[Xu, Like]

Hi Aditya,

On "Comet Lake", the answer will also be (unofficially) negative.
You may preferentially focus on the Small Core (Atom) or Hybrid Processors.

Ref: 
https://raw.githubusercontent.com/torvalds/linux/master/arch/x86/include/asm/intel-family.h

On 2021/3/3 3:59, Aditya Basu wrote:
> Thanks a lot for the information. From what I see, the Atom P series
> are server-grade processors.
>
> Would you happen to know if any Desktop/Workstation processors (ex.
> 10th gen i9) also support this feature?
> Specifically, I'm referring to Comet Lake, here --
>
> https://ark.intel.com/content/www/us/en/ark/products/codename/90354/comet-lake.html
>
> Aditya
>
>
> Aditya
>
> On Mon, Mar 1, 2021 at 8:16 PM Xu, Like <like.xu@intel.com> wrote:
>> On 2021/3/2 2:48, Aditya Basu wrote:
>>> Hi all,
>>> I am a PhD student at the Pennsylvania State University. For my
>>> current project, I am trying to run Intel Processor Trace (PT) inside
>>> a Guest VM. Specifically, I want to run KVM in the "Host-Guest mode"
>>> as stated in the following bug:
>>> https://bugzilla.kernel.org/show_bug.cgi?id=201565
>>>
>>> However, I *cannot* find an Intel processor that supports this mode. I
>>> have tried using Intel's i7-7700 and i7-9700k processors. Based on my
>>> findings, the problem seems to be that bit 24 (PT_USE_GPA) of
>>> MSR_IA32_VMX_PROCBASED_CTLS2 (high) is reported as 0 by the processor.
>>> Hence, KVM seems to force pt_mode to 0 (or PT_MODE_HOST).
>> You may try the Intel Atom® Processor P* Series.
>>
>> https://ark.intel.com/content/www/us/en/ark/products/series/29035/intel-atom-processor.html?wapkw=Atom#@Server
>>
>>> I would appreciate any pointers that someone might have regarding the
>>> above. Specifically, I want to find an Intel processor that supports
>>> running Intel PT in "Host-Guest mode".
>>>
>>> Regards,
>>>
>>> Aditya Basu
>>> PhD Student in CSE
>>> Pennsylvania State University
>>> https://www.adityabasu.me/