From: Alexander Graf <agraf@suse.de>
To: Paul Mackerras <paulus@samba.org>
Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH 6/7] KVM: PPC: Book3S HV: Work around POWER8 performance monitor bugs
Date: Sun, 25 May 2014 10:07:40 +0000 [thread overview]
Message-ID: <5381C0EC.70208@suse.de> (raw)
In-Reply-To: <1400919721-14264-7-git-send-email-paulus@samba.org>
On 24.05.14 10:22, Paul Mackerras wrote:
> This adds workarounds for two hardware bugs in the POWER8 performance
> monitor unit (PMU), both related to interrupt generation. The effect
> of these bugs is that PMU interrupts can get lost, leading to tools
> such as perf reporting fewer counts and samples than they should.
>
> The first bug relates to the PMAO (perf. mon. alert occurred) bit in
> MMCR0; setting it should cause an interrupt, but doesn't. The other
> bug relates to the PMAE (perf. mon. alert enable) bit in MMCR0.
> Setting PMAE when a counter is negative and counter negative
> conditions are enabled to cause alerts should cause an alert, but
> doesn't.
>
> The workaround for the first bug is to create conditions where a
> counter will overflow, whenever we are about to restore a MMCR0
> value that has PMAO set (and PMAO_SYNC clear). The workaround for
> the second bug is to freeze all counters using MMCR2 before reading
> MMCR0.
>
> Signed-off-by: Paul Mackerras <paulus@samba.org>
I seriously hope you're actively working on converting this whole file
to C code :).
Alex
WARNING: multiple messages have this Message-ID (diff)
From: Alexander Graf <agraf@suse.de>
To: Paul Mackerras <paulus@samba.org>
Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH 6/7] KVM: PPC: Book3S HV: Work around POWER8 performance monitor bugs
Date: Sun, 25 May 2014 12:07:40 +0200 [thread overview]
Message-ID: <5381C0EC.70208@suse.de> (raw)
In-Reply-To: <1400919721-14264-7-git-send-email-paulus@samba.org>
On 24.05.14 10:22, Paul Mackerras wrote:
> This adds workarounds for two hardware bugs in the POWER8 performance
> monitor unit (PMU), both related to interrupt generation. The effect
> of these bugs is that PMU interrupts can get lost, leading to tools
> such as perf reporting fewer counts and samples than they should.
>
> The first bug relates to the PMAO (perf. mon. alert occurred) bit in
> MMCR0; setting it should cause an interrupt, but doesn't. The other
> bug relates to the PMAE (perf. mon. alert enable) bit in MMCR0.
> Setting PMAE when a counter is negative and counter negative
> conditions are enabled to cause alerts should cause an alert, but
> doesn't.
>
> The workaround for the first bug is to create conditions where a
> counter will overflow, whenever we are about to restore a MMCR0
> value that has PMAO set (and PMAO_SYNC clear). The workaround for
> the second bug is to freeze all counters using MMCR2 before reading
> MMCR0.
>
> Signed-off-by: Paul Mackerras <paulus@samba.org>
I seriously hope you're actively working on converting this whole file
to C code :).
Alex
next prev parent reply other threads:[~2014-05-25 10:07 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-24 8:21 [PATCH 0/7] Bug fixes for HV KVM Paul Mackerras
2014-05-24 8:21 ` Paul Mackerras
2014-05-24 8:21 ` [PATCH 1/7] KVM: PPC: Book3S: Add ONE_REG register names that were missed Paul Mackerras
2014-05-24 8:21 ` Paul Mackerras
2014-05-24 8:21 ` [PATCH 2/7] KVM: PPC: Book3S: Move KVM_REG_PPC_WORT to an unused register number Paul Mackerras
2014-05-24 8:21 ` Paul Mackerras
2014-05-24 8:21 ` [PATCH 3/7] KVM: PPC: Book3S HV: Fix check for running inside guest in global_invalidates() Paul Mackerras
2014-05-24 8:21 ` Paul Mackerras
2014-05-24 8:21 ` [PATCH 4/7] KVM: PPC: Book3S HV: Fix dirty map for hugepages Paul Mackerras
2014-05-24 8:21 ` Paul Mackerras
2014-05-25 10:00 ` Alexander Graf
2014-05-25 10:00 ` Alexander Graf
2014-05-26 3:30 ` Paul Mackerras
2014-05-26 3:30 ` Paul Mackerras
2014-05-24 8:21 ` [PATCH 5/7] KVM: PPC: Book3S HV: Make sure we don't miss dirty pages Paul Mackerras
2014-05-24 8:21 ` Paul Mackerras
2014-05-24 8:22 ` [PATCH 6/7] KVM: PPC: Book3S HV: Work around POWER8 performance monitor bugs Paul Mackerras
2014-05-24 8:22 ` Paul Mackerras
2014-05-25 10:07 ` Alexander Graf [this message]
2014-05-25 10:07 ` Alexander Graf
2014-05-24 8:22 ` [PATCH 7/7] KVM: PPC: Book3S HV: Fix machine check delivery to guest Paul Mackerras
2014-05-24 8:22 ` Paul Mackerras
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