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SubjectRe: [PATCH 08/11] perf tool: precise mode requires exclude_guest
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On Wed, 2012-07-25 at 23:16 -0600, David Ahern wrote:

> Peter's patch (see https://lkml.org/lkml/2012/7/9/298) changes kernel
> side to require the use of exclude_guest if the precise modifier is
> used, returning -EOPNOTSUPP if exclude_guest is not set. This patch goes
> after the user experience: Today if a user specifies -e <event>:p all
> other modifiers are reset - including exclude_guest. Going forward we
> need :p to imply :pH if a user has not specified a GH modifer.
>
> We could do nothing and handle the unsupported error and try setting the
> exclude_guest option - like perf handles other new parameters. But
> EOPNOTSUPP is not uniquely tied to this error -- e.g., it could be the
> BTS is not supported (:pp). Also, we have no easy way to discriminate :p
> from :pG or :pGH. It seems to me perf should not silently undo a user
> request on the modifier, but inform the user the request is wrong. For
> example if a user request -e cycles:pG it should not be silently turned
> into :pH.
>
> And then yesterday, Robert stated that none of the exclude_xxxx
> modifiers can be set for the AMD if the precise modifier is used, so we
> cannot blindly set exclude_guest if precise_ip is set.
>
> So, seems to me perf need's one action for Intel processors and another
> for AMD.

No, we just need to teach the IBS code about SVM enter/exit.



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