Messages in this thread | | | Subject | Re: [PATCH] perf/intel: Remove Perfmon-v4 counter_freezing support | From | Paolo Bonzini <> | Date | Tue, 26 Jan 2021 10:51:39 +0100 |
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On 11/11/20 03:42, Xu, Like wrote: > Hi Peter, > > On 2020/11/11 4:52, Stephane Eranian wrote: >> On Tue, Nov 10, 2020 at 7:37 AM Peter Zijlstra<peterz@infradead.org> >> wrote: >>> On Tue, Nov 10, 2020 at 04:12:57PM +0100, Peter Zijlstra wrote: >>>> On Mon, Nov 09, 2020 at 10:12:37AM +0800, Like Xu wrote: >>>>> The Precise Event Based Sampling(PEBS) supported on Intel Ice Lake >>>>> server >>>>> platforms can provide an architectural state of the instruction >>>>> executed >>>>> after the instruction that caused the event. This patch set enables >>>>> the >>>>> the PEBS via DS feature for KVM (also non) Linux guest on the Ice >>>>> Lake. >>>>> The Linux guest can use PEBS feature like native: >>>>> >>>>> # perf record -e instructions:ppp ./br_instr a >>>>> # perf record -c 100000 -e instructions:pp ./br_instr a >>>>> >>>>> If the counter_freezing is not enabled on the host, the guest PEBS >>>>> will >>>>> be disabled on purpose when host is using PEBS facility. By default, >>>>> KVM disables the co-existence of guest PEBS and host PEBS. > Thanks Stephane for clarifying the use cases for Freeze-on-[PMI|Overflow]. > > Please let me express it more clearly. > > The goal of the whole patch set is to enable guest PEBS, regardless of > whether the counter_freezing is frozen or not. By default, it will not > support both the guest and the host to use PEBS at the same time. > > Please continue reviewing the patch set, especially for the slow path > we proposed this time and related host perf changes: > > - add intel_pmu_handle_guest_pebs() to __intel_pmu_pebs_event(); > - add switch MSRs (PEBS_ENABLE, DS_AREA, DATA_CFG) to > intel_guest_get_msrs(); > - the construction of incoming parameters for > perf_event_create_kernel_counter(); > > I believe if you understand the general idea, the comments will be very > valuable.
What is the state of this work? I was expecting a new version that doesn't use counter_freezing. However, I see that counter_freezing is still in there, so this patch from Peter has never been applied.
Paolo
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