Messages in this thread | | | Date | Tue, 4 May 2021 14:13:44 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86/events/amd/iommu: Fix invalid Perf result due to IOMMU PMC power-gating |
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On Tue, May 04, 2021 at 06:58:29PM +0700, Suthikulpanit, Suravee wrote: > Peter, > > On 5/4/2021 4:39 PM, Peter Zijlstra wrote: > > On Tue, May 04, 2021 at 01:52:36AM -0500, Suravee Suthikulpanit wrote: > > > > > 2. Since AMD IOMMU PMU does not support interrupt mode, the logic > > > can be simplified to always start counting with value zero, > > > and accumulate the counter value when stopping without the need > > > to keep track and reprogram the counter with the previously read > > > counter value. > > > > This relies on the hardware counter being the full 64bit wide, is it? > > > > The HW counter value is 48-bit. Not sure why it needs to be 64-bit? > I might be missing some points here? Could you please describe?
How do you deal with the 48bit overflow if you don't use the interrupt?
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