linux-kernel - Re: [PATCH v4] perf: arm_spe: Properly set hw.state on failures

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Message-ID: <177014771123.2668461.9075722971112388662.b4-ty@kernel.org>
Date: Tue,  3 Feb 2026 20:29:02 +0000
From: Will Deacon <will@...nel.org>
To: Mark Rutland <mark.rutland@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	James Clark <james.clark@...aro.org>,
	Leo Yan <leo.yan@....com>
Cc: catalin.marinas@....com,
	kernel-team@...roid.com,
	Will Deacon <will@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] perf: arm_spe: Properly set hw.state on failures

On Tue, 03 Feb 2026 14:40:43 +0000, Leo Yan wrote:
> When arm_spe_pmu_next_off() fails to calculate a valid limit, it returns
> zero to indicate that tracing should not start.  However, the caller
> arm_spe_perf_aux_output_begin() does not propagate this failure by
> updating hwc->state, cause the error to be silently ignored by upper
> layers.
> 
> Because hwc->state remains zero after a failure, arm_spe_pmu_start()
> continues to programs filter registers unnecessarily.  The driver
> still reports success to the perf core, so the core assumes the SPE
> event was enabled and proceeds to enable other events.  This breaks
> event group semantics: SPE is already stopped while other events in the
> same group are enabled.
> 
> [...]

Applied to arm64 (for-next/core), thanks!

[1/1] perf: arm_spe: Properly set hw.state on failures
      https://git.kernel.org/arm64/c/283182c1c239

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev