From: Mark Brown <broonie@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, will@kernel.org,
catalin.marinas@arm.com, mark.rutland@arm.com,
James Clark <james.clark@arm.com>, Rob Herring <robh@kernel.org>,
Marc Zyngier <maz@kernel.org>,
Suzuki Poulose <suzuki.poulose@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
linux-perf-users@vger.kernel.org
Subject: Re: [PATCH V9 00/10] arm64/perf: Enable branch stack sampling
Date: Fri, 24 Mar 2023 11:40:46 +0000 [thread overview]
Message-ID: <ZB2MPqqBjzyaMlrd@sirena.org.uk> (raw)
In-Reply-To: <4665d03f-b801-679c-0b52-c426404284b9@arm.com>
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On Fri, Mar 24, 2023 at 08:50:32AM +0530, Anshuman Khandual wrote:
> On 3/23/23 18:24, Mark Brown wrote:
> > On Thu, Mar 23, 2023 at 09:55:47AM +0530, Anshuman Khandual wrote:
> >> By default entire SYS_HFGITR_EL2 is set as cleared during init and that would
> >> prevent a guest from using BRBE.
> > It should prevent the host as well shouldn't it?
> In a EL2 host environment, BRBE is being enabled either in EL2 (kernel/hv) or
> in EL0 (user space), it never gets enabled on EL1. Moreover BRBIALL/BRBINJ
> instructions are always executed while being inside EL2 (kernel/hv). Hence how
> could these instructions cause trap in EL2 ?
Ah, I see - I didn't realise this couldn't run at EL1.
> > Yes, looks roughly what I'd expect.
> I could send an stand alone patch after your latest series [1], which disables
> BRBINJ/BRBIALL instruction trap in EL2 to enable BRBE usage in the guest.
Sounds resaonable enough to me.
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next prev parent reply other threads:[~2023-03-24 11:40 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-15 5:14 [PATCH V9 00/10] arm64/perf: Enable branch stack sampling Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 01/10] drivers: perf: arm_pmu: Add new sched_task() callback Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 02/10] arm64/perf: Add BRBE registers and fields Anshuman Khandual
2023-04-12 8:32 ` Yang Shen
2023-05-15 6:22 ` Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 03/10] arm64/perf: Add branch stack support in struct arm_pmu Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 04/10] arm64/perf: Add branch stack support in struct pmu_hw_events Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 05/10] arm64/perf: Add branch stack support in ARMV8 PMU Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 06/10] arm64/perf: Enable branch stack events via FEAT_BRBE Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 07/10] arm64/perf: Add PERF_ATTACH_TASK_DATA to events with has_branch_stack() Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 08/10] arm64/perf: Add struct brbe_regset helper functions Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 09/10] arm64/perf: Implement branch records save on task sched out Anshuman Khandual
2023-03-15 5:14 ` [PATCH V9 10/10] arm64/perf: Implement branch records save on PMU IRQ Anshuman Khandual
2023-05-23 14:39 ` James Clark
2023-05-23 14:51 ` James Clark
2023-05-24 3:10 ` Anshuman Khandual
2023-03-21 19:02 ` [PATCH V9 00/10] arm64/perf: Enable branch stack sampling Mark Brown
2023-03-23 4:25 ` Anshuman Khandual
2023-03-23 12:54 ` Mark Brown
2023-03-24 3:20 ` Anshuman Khandual
2023-03-24 11:40 ` Mark Brown [this message]
2023-04-11 13:03 ` Will Deacon
2023-05-15 6:24 ` Anshuman Khandual
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