From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Michael Ellerman <michael@ellerman.id.au>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] powerpc: Partial revert of "Context switch more PMU related SPRs"
Date: Mon, 10 Jun 2013 09:48:17 +0530 [thread overview]
Message-ID: <51B55389.1080306@linux.vnet.ibm.com> (raw)
In-Reply-To: <1370491416-1807-1-git-send-email-michael@ellerman.id.au>
On 06/06/2013 09:33 AM, Michael Ellerman wrote:
> In commit 59affcd I added context switching of more PMU SPRs, because
> they are potentially exposed to userspace on Power8. However despite me
> being a smart arse in the commit message it's actually not correct. In
> particular it interacts badly with a global perf record.
Could you please explain how it would interact badly with a global perf record.
If any user space try to mess around with the MMCR* registers itself, it would
definitely interfere with the kernel's own PMU config going on during perf record.
But thats how it works. So when we are actually dealing with MMCR* registers
directly, we should not invoke "perf record" session which can potential run on
the same PMU.
Regards
Anshuman
prev parent reply other threads:[~2013-06-10 4:19 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-06 4:03 [PATCH] powerpc: Partial revert of "Context switch more PMU related SPRs" Michael Ellerman
2013-06-10 4:18 ` Anshuman Khandual [this message]
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