[Xen-devel] Re: [PATCH] Enable Core 2 Duo Performance Counters in HVM guest

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

 * Don’t define new MSR macros – use the existing ones (or fixup the eixsting ones to have better names if you really think that is necessary, although I doubt it is in this case).

 * Some of the indentation is rather wacky.

 * Poking the LVTPC as a one-off event only when the VCPU writes its virtual LVTPC is not going to fly. What if the VCPU is subsequently migrated to a different physical CPU? In any case the LVTPC is a shared resource that needs synchronised access via e.g., context switching or mutual exclusion (see the next point below).

 * How does this interact with, for example, xenoprof? Ideally we should be able to run xenoprof and this concurrently over disjoint subsets of domains. At the very least xenoprof and this patch should avoid stomping on each other by implementing some form of mutual exclusion. Probably some resource sharing (e.g., the PMC interrupt vector) also is possible. I expect this will require some design thought, but unfortunately that is the price for being second into the tree.

 * Impact on save/restore to/from Core-2 processors: has this been tested at all?

 -- Keir

On 11/12/07 10:06, "Shan, Haitao" <haitao.shan@xxxxxxxxx> wrote:

> Hi, Keir, 
>
> Currently, HVM guests do not have access to performance counters. So it is not possible to use performance analyzer software such as vtune in HVM guest to analyze programme performance. Other usage of performance counters , for example, the NMI watchdog, won't function either.
>
> This patch will enable performance counters in HVM guest. Currently, only Core 2 Duo is implemented. Tests are carried out using Intel Vtune Performance Analyzer in Windows XP Professional with 2 vcpus.
>
> There are some notes at the beginning of the patch, describing implementation choices in this patch. 
>
> Signed-off-by:    Haitao Shan <haitao.shan@xxxxxxxxx> 
>  <<pmu.patch>> 
>
> Best Regards 
> Haitao Shan 




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