From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8A112CFD345 for ; Mon, 24 Nov 2025 18:48:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=NNVrYCsyAm8UHi1MQl7sBfSQXgOpBYYtQN3G2pleKGk=; b=IeNcUQrnxTBagKAXjT2IOnOUct /nWGE9w+rDzHvCKNGysb07NpaL8JBIjBo0pHolUNdD2yTo1hMxKpGozPl4DPMnvjywjpFqgCBbndF CzDERiOPssCAEBHkD4/DBj8JIA4r66dOjudZokksKMF+VWJdlXLPCRtqS1HDhXPz4NP5kwSPckwL6 NPDZWW0ernbZgAejEsWSTN8wwEkOPT9bJXri7W8a0UHVrtK79TtrCGB8NriyZqbEty2sy4H1Kl1xm uK/Vfgb/1gNW9+D8Zrp8l7DtNTBt5K3annCk3LCHKgXDiJEUttDtMv/s+LLoADlvDQYI2bHKxxB+i Tnu/L0tw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNbbq-0000000CCI1-2VVx; Mon, 24 Nov 2025 18:48:22 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNbbo-0000000CCHP-0BBE for linux-arm-kernel@lists.infradead.org; Mon, 24 Nov 2025 18:48:21 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E0F7C1477; Mon, 24 Nov 2025 10:48:09 -0800 (PST) Received: from localhost (e132581.arm.com [10.1.196.87]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F36293F86F; Mon, 24 Nov 2025 10:48:16 -0800 (PST) Date: Mon, 24 Nov 2025 18:48:15 +0000 From: Leo Yan To: Will Deacon Cc: Mark Rutland , Alexandru Elisei , James Clark , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] perf: arm_spe: Correct setting the PERF_HES_STOPPED flag Message-ID: <20251124184815.GC724103@e132581.arm.com> References: <20251110-arm_spe_fix_truncated_flag-v2-0-a629740985cc@arm.com> <20251110-arm_spe_fix_truncated_flag-v2-1-a629740985cc@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251124_104820_203618_256B7B2A X-CRM114-Status: GOOD ( 27.91 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Nov 24, 2025 at 04:14:23PM +0000, Will Deacon wrote: > On Mon, Nov 10, 2025 at 04:28:31PM +0000, Leo Yan wrote: > > In arm_spe_perf_aux_output_begin(), if the calculation of limit fails > > and arm_spe_pmu_next_off() returns zero, the driver misses to set the > > PERF_HES_STOPPED flag for the event. As a result, hwc->state does not > > reflect the latest state, which can mislead subsequent operations. > > > > Validate the limit when exiting the function: if the limit is 0, > > that tracing is disabled, set the PERF_HES_STOPPED flag accordingly. > > > > Fixes: d5d9696b0380 ("drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension") > > Signed-off-by: Leo Yan > > --- > > drivers/perf/arm_spe_pmu.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c > > index fa50645feddadbea5dc1e404f80f62cf5aa96fd4..fc8f908c2c3a270f2d1ae574c2badb1fbcf51484 100644 > > --- a/drivers/perf/arm_spe_pmu.c > > +++ b/drivers/perf/arm_spe_pmu.c > > @@ -597,7 +597,6 @@ static void arm_spe_perf_aux_output_begin(struct perf_output_handle *handle, > > /* Start a new aux session */ > > buf = perf_aux_output_begin(handle, event); > > if (!buf) { > > - event->hw.state |= PERF_HES_STOPPED; > > /* > > * We still need to clear the limit pointer, since the > > * profiler might only be disabled by virtue of a fault. > > @@ -608,15 +607,19 @@ static void arm_spe_perf_aux_output_begin(struct perf_output_handle *handle, > > > > limit = buf->snapshot ? arm_spe_pmu_next_snapshot_off(handle) > > : arm_spe_pmu_next_off(handle); > > - if (limit) > > - limit |= PMBLIMITR_EL1_E; > > + if (!limit) > > + goto out_write_limit; > > Is 'limit == 0' always indicative of an error, even in snapshot mode? Yes, the 'limit' would never be zero unless an error occurs. > If __arm_spe_pmu_next_off() fails, it will call perf_aux_output_end() > with the TRUNCATED flag set, which should then disable the event > via arm_spe_pmu_del() and update the state there. > > Is that not happening? Correct. However, this patch is not for the flow you mentioned. If an error is returned from arm_spe_pmu_next_off(), because hw.state is not set to PERF_HES_STOPPED, the caller arm_spe_pmu_start() cannot detect error properly: arm_spe_pmu_start() { ... hwc->state = 0; arm_spe_perf_aux_output_begin(handle, event); // Miss to set hwc->state // for error case. if (hwc->state) // Fail to detect error. return; reg = arm_spe_event_to_pmsfcr(event); write_sysreg_s(reg, SYS_PMSFCR_EL1); ... } This patch consolidates arm_spe_perf_aux_output_begin() to always set the PERF_HES_STOPPED flag for errors, ensuring consistent error handling. A side effect is that arm_spe_pmu_del() will skip disabling buffer unit when "hwc->state==PERF_HES_STOPPED". This is why we need the patch 02 to explicitly disable the buffer unit in interrupt handler. Thanks, Leo