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SubjectRe: [PATCH 9/9] x86, perf: Move PMU ACK after LBR read
On Mon, May 11, 2015 at 9:23 AM, Peter Zijlstra <> wrote:
> On Sun, May 10, 2015 at 12:22:47PM -0700, Andi Kleen wrote:
>> From: Andi Kleen <>
>> With Arch Perfmon v4 the PMU ack unfreezes the LBRs. So we need to do
>> the PMU ack after the LBR reading, otherwise the LBRs would be polluted by the
>> PMI handler.
> Hmm, we should move these last three patches before the SKL enablement
> patch no, otherwise things will misbehave -- say a bisection lands in
> between.
> /me shuffles patches.
>> This is a minimal change. In principle the ACK could be moved much later.
> Right, so the more complete change would be to use the new and improved
> FREEZE_ON_PMI and reenable both the LBRs and the CTRs with the
> Does it make sense to have a new handle_irq() routine for that?

Were we not already using FREEZE_ON_PMI with LBR (except for one
erratum on HSW)?
It would make sense to me to have an "optimized" and clean handle_irq
for the newer PMU.
We the caveat that any change to the core of it would now have to be done twice.

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