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Re: [Xen-devel] [PATCH RESEND v1 0/7] Intel Processor Trace virtulization enabling

> On Tue, Jan 16, 2018 at 02:12:26AM +0800, Luwei Kang wrote:
> > Hi All,
> >
> > Here is a patch-series which adding Processor Trace enabling in XEN guest. 
> > You can get It's software developer manuals from:
> > https://software.intel.com/sites/default/files/managed/c5/15/architect
> > ure-instruction-set-extensions-programming-reference.pdf
> Now Chapter 4.

Yes, will update this description. Thanks.

> >
> > Introduction:
> > Intel Processor Trace (Intel PT) is an extension of Intel Architecture that 
> > captures information about software execution using
> dedicated hardware facilities that cause only minimal performance 
> perturbation to the software being traced. Details on the Intel PT
> infrastructure and trace capabilities can be found in the Intel 64 and IA-32 
> Architectures Software Developer’s Manual, Volume 3C.
> >
> > The suite of architecture changes serve to simplify the process of 
> > virtualizing Intel PT for use by a guest software. There are two
> primary elements to this new architecture support for VMX support 
> improvements made for Intel PT.
> > 1. Addition of a new guest IA32_RTIT_CTL value field to the VMCS.
> >   — This serves to speed and simplify the process of disabling trace on VM 
> > exit, and restoring it on VM entry.
> > 2. Enabling use of EPT to redirect PT output.
> >   — This enables the VMM to elect to virtualize the PT output buffer using 
> > EPT. In this mode, the CPU will treat PT output
> addresses as Guest Physical Addresses (GPAs) and translate them using EPT. 
> This means that Intel PT output reads (of the ToPA
> table) and writes (of trace output) can cause EPT violations, and other 
> output events.
> >
> How does one test this functionality in Linux? As in does 'perf' take 
> advantage of the Processor Trace functionality?

We can test this feature by "perf" tools in Linux. 

Luwei Kang
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