From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793979608; b=or+3NaBbaZ3/wKuWhqGIb3WtuspYN9O0tPlwitdPu8k8y1sNSeUAAML0yeyMU8YLUb2I ArbTXKJ+LtA26vaKF0foRT5KxuUVNzpRaUNBiRXegM54w3adnJm8cQTkZMg+u+9A2Yxkm AA95loflCYqogpJb1v9QtvhGT+9KZ4VqqHNIE0hVhU72KDbXvvFOpXHihp3KQY4VUSrm2 P2zYwTCIVVHqqywFLkdfIPkVygOfoKFIJjhUMzmtBjlES7XNXnXzG7U9ftfISesAkXrgZ GjoQnypdYVQM2NNQud7tgzfUfJeVFPfDRH719NBhZe4e9hkKLFB0QC7t1sis1L5BbBQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793979608; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=GjZxu266jNxwcR9mDbLVKfmtb9ofuqlgjo6mMVq48Ow=; b=yE9noc+l+jG0KObbf8p+vmFTfypO+7px8RmV3QHi7uUudBhzMtX9g7yvuOCrKeMWvWrr DIS3yjS6lPG1qvXSe/EGnrt2crIqwHCZXz2VtC7LjSHZtDdebpIZDqtl14wKWkFxKL6Sa YKPGMCRy5Yftp2tkncrHqfcvxRefBRCvsEHNs94auG0HkflMufm9B1+0gdc6U9q0wwWyi 54s02fvvxfT9Bx8517271frRf2tKOxs3SM7wJ07gWWpCrqXqkvThyTglYBDLi+Jsedtvk xZ/hjIcsqziIbea7dqVJ1PiQIzicxQ7aySgSpszfEZKR0pCQ2eggGJb547C0kwO2oZQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=b9PcMiN9; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EB29C606A332 for ; Fri, 6 Nov 2026 15:40:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=b9PcMiN9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6016B1F0089F; Fri, 6 Nov 2026 15:40:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793979607; bh=GjZxu266jNxwcR9mDbLVKfmtb9ofuqlgjo6mMVq48Ow=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=b9PcMiN9Eyh6Y1nHv0j8ZdtKXqS+JtGE65/ANJNbJxbJakhtJ88RjlN98bI8HU3MJ 2CGoi5X4r3x8NFx82QCEfz9ZF+n6tqxfENn2pXm0zhkavCSf6MvoiF5IElJVSv7EEf Eek+g0ERAlNMXzeYYAj+qJZS8hm06GrsgqDsQQdQ8pgJ/BU5JTuWsaEll7ToGPztdH 07gCnA0qfIXDVyYysvpS6PnDcyCDCD9ubwHf64vWiYcGUHG6w8LgUAIWQ94mD34Qj+ KmXqEB3O3CYD1DGEhfcARS/e8Q2S/9nnbnVEQ6HRk8viYUoPpWT1TkZB3kZmoronwG n7MtlykGkdRjA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v3 2/3] powerpc/perf: Update prev_count of event to get accurate values Reply-To: sashiko-reviews@lists.linux.dev To: "Gautam Menghani" Cc: kvm@vger.kernel.org In-Reply-To: <20261106153136.330165-3-gautam@linux.ibm.com> References: <20261106153136.330165-1-gautam@linux.ibm.com> <20261106153136.330165-3-gautam@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 06 Nov 2026 15:40:07 +0000 X-Mailing-List: kvm@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Thank you for your contribution! Sashiko AI review found 1 potential issue to consider: - [Low] powerpc/perf: dead store to prev_data from local64_read() in vpa_pmu_read() -- commit e6b6a01ca205d4ad136547505bcf1dcf984b82ba Author: Gautam Menghani powerpc/perf: Update prev_count of event to get accurate values This commit updates event->hw.prev_count in vpa_pmu_read() using local64_xchg() so that consecutive counter reads accumulate only the delta since the last read. > diff --git a/arch/powerpc/perf/vpa-pmu.c b/arch/powerpc/perf/vpa-pmu.c > index 01d9196fcb0f6..3296877eb317b 100644 > --- a/arch/powerpc/perf/vpa-pmu.c > +++ b/arch/powerpc/perf/vpa-pmu.c > @@ -132,6 +132,7 @@ static void vpa_pmu_read(struct perf_event *event) > =20 > prev_data =3D local64_read(&event->hw.prev_count); > new_data =3D get_counter_data(event); > + prev_data =3D local64_xchg(&event->hw.prev_count, new_data); [Severity: Low] Can the earlier local64_read(&event->hw.prev_count) call be dropped now that local64_xchg() unconditionally overwrites prev_data before it is used? Because local64_read() expands to a volatile READ_ONCE() load, the compiler cannot elide the redundant read on every vpa_pmu_read() call. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261106153136.3301= 65-1-gautam@linux.ibm.com?part=3D2