From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3A19F3B9D9E for ; Tue, 6 Oct 2026 08:51:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791276683; cv=none; b=HrfohWjMUxYyN5bOO/nNLzfx+JouBfhjFBYkF0TVGUcbF0YxOadg7B56VG8wDHNR49G+nfKovHk8GbwygzWqUtidyXNRkarMjXBkruY1I0f1R2B9x9932vKHYmGcUwA9ahvUIcUu0X5Id0fYrSJ/RGc+lvJ7TblydJES5lypjH0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791276683; c=relaxed/simple; bh=esKVpiK8T5DHRr86gE+NWx03wG+K05UVkNwP7QblqGo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ixUg6glv1pwVVBqsoThinNSP4Kax71omIiqgM++FvoSDR1l3kGJ9CmPj73/R9j5mgf5tgtMttYwayjWzqWiwJqv2oupS9ILYn3XMvAH1Sl4fOgJ9kk6QLNCR9++XQldJ+S3WTuq8vkW03gHe2Rh62wd2WbkvKESY47FwAO6gcBo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=WSSubnG+; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="WSSubnG+" 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 1D060152B; Tue, 6 Oct 2026 01:51:17 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4B8693F86F; Tue, 6 Oct 2026 01:51:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1791276680; bh=esKVpiK8T5DHRr86gE+NWx03wG+K05UVkNwP7QblqGo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WSSubnG+HqMxG7YcQZA2IXl+oJqLdYkwtK1H6FnWYksTIWCuhXosjpXKCYmVgrPAK AyMajpmk8FwfAkAJjVehORYfsPC1FlICPOXm/Grpo7PGo+RVjHW7E4wSt0pVaRFUOn pyhaZOGjYSzMAkpJIKSjXjgO+OrByrxFhcqfECkk= Date: Tue, 6 Oct 2026 10:51:16 +0200 From: Beata Michalska To: Sasha Levin Cc: stable@vger.kernel.org, Vladimir Murzin , Will Deacon Subject: Re: [PATCH 6.12.y 1/2] arm64: errata: Factor out broken AMU const counter cap Message-ID: References: <2026100501-unsubtle-blank-50b6@gregkh> <20261006002934.3618253-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261006002934.3618253-1-sashal@kernel.org> LGTM. Thank you. --- BR Beata On Mon, Oct 05, 2026 at 08:29:47PM -0400, Sasha Levin wrote: > From: Beata Michalska > > [ Upstream commit 573371caf7aea8582212da81dcead2c3f48fac4b ] > > Move the workaround from the erratum 2457168-specific cpucap to a generic > broken AMU constant-counter one. This keeps the existing Cortex-A510 > handling unchanged while allowing other errata with similar AMU constant > counter issue to share the capability bit and call sites. > > Signed-off-by: Beata Michalska > Reviewed-by: Vladimir Murzin > Signed-off-by: Will Deacon > > Omit the comment-only update to the paired AMU counter reader, which > is absent here. Retain the shared capability, CPU matching list, and > the checks in the existing counter-read and frequency-invariance paths. > > Stable-dep-of: 45f730467987 ("arm64: errata: Add Cortex-A725 erratum 3821522 workaround") > Signed-off-by: Sasha Levin > --- > arch/arm64/Kconfig | 8 ++++++++ > arch/arm64/kernel/cpu_errata.c | 20 ++++++++++++++------ > arch/arm64/kernel/cpufeature.c | 2 +- > arch/arm64/kernel/topology.c | 2 +- > arch/arm64/tools/cpucaps | 2 +- > 5 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 938bf2f96b1a8..d2901607b4f9e 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1023,9 +1023,17 @@ config ARM64_ERRATUM_1902691 > > If unsure, say Y. > > +config ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT > + bool > + # Targeting errata affecting AMEVCNTR01, the AMU constant counter. > + # On affected CPUs the counter may not increment at the expected rate, > + # making it unreliable. As a result, AMU users should treat it as > + # unavailable rather than relying on misleading counter values. > + > config ARM64_ERRATUM_2457168 > bool "Cortex-A510: 2457168: workaround for AMEVCNTR01 incrementing incorrectly" > depends on ARM64_AMU_EXTN > + select ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT > default y > help > This option adds the workaround for ARM Cortex-A510 erratum 2457168. > diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c > index 80e47d3e86af4..1dc2373fc1b9c 100644 > --- a/arch/arm64/kernel/cpu_errata.c > +++ b/arch/arm64/kernel/cpu_errata.c > @@ -259,6 +259,16 @@ static const struct arm64_cpu_capabilities arm64_repeat_tlbi_list[] = { > }; > #endif > > +#ifdef CONFIG_ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT > +static const struct midr_range workaround_amu_constcnt_list[] = { > +#ifdef CONFIG_ARM64_ERRATUM_2457168 > + /* Cortex-A510 r0p0-r1p1 */ > + MIDR_RANGE(MIDR_CORTEX_A510, 0, 0, 1, 1), > +#endif > + {} > +}; > +#endif /* CONFIG_ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT */ > + > #ifdef CONFIG_CAVIUM_ERRATUM_23154 > static const struct midr_range cavium_erratum_23154_cpus[] = { > MIDR_ALL_VERSIONS(MIDR_THUNDERX), > @@ -750,14 +760,12 @@ const struct arm64_cpu_capabilities arm64_errata[] = { > ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 2) > }, > #endif > -#ifdef CONFIG_ARM64_ERRATUM_2457168 > +#ifdef CONFIG_ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT > { > - .desc = "ARM erratum 2457168", > - .capability = ARM64_WORKAROUND_2457168, > + .desc = "Broken AMU AMEVCNTR01 (const counter)", > + .capability = ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT, > .type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE, > - > - /* Cortex-A510 r0p0-r1p1 */ > - CAP_MIDR_RANGE(MIDR_CORTEX_A510, 0, 0, 1, 1) > + CAP_MIDR_RANGE_LIST(workaround_amu_constcnt_list) > }, > #endif > #ifdef CONFIG_ARM64_ERRATUM_2038923 > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 8246015fd2d73..ae4782ce523a6 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -2070,7 +2070,7 @@ static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap) > cpumask_set_cpu(smp_processor_id(), &amu_cpus); > > /* 0 reference values signal broken/disabled counters */ > - if (!this_cpu_has_cap(ARM64_WORKAROUND_2457168)) > + if (!this_cpu_has_cap(ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT)) > update_freq_counters_refs(); > } > } > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > index cb180684d10d5..d21b4e963f6b7 100644 > --- a/arch/arm64/kernel/topology.c > +++ b/arch/arm64/kernel/topology.c > @@ -271,7 +271,7 @@ static void cpu_read_constcnt(void *val) > * the counter is disabled. A return value of 0 at counter read is > * properly handled as an error case by the users of the counter. > */ > - *(u64 *)val = this_cpu_has_cap(ARM64_WORKAROUND_2457168) ? > + *(u64 *)val = this_cpu_has_cap(ARM64_WORKAROUND_BROKEN_AMU_CONSTCNT) ? > 0UL : read_constcnt(); > } > > diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps > index eedb5acc21ed9..edb2e35e5e7ee 100644 > --- a/arch/arm64/tools/cpucaps > +++ b/arch/arm64/tools/cpucaps > @@ -85,7 +85,6 @@ WORKAROUND_1902691 > WORKAROUND_2038923 > WORKAROUND_2064142 > WORKAROUND_2077057 > -WORKAROUND_2457168 > WORKAROUND_2645198 > WORKAROUND_2658417 > WORKAROUND_AMPERE_AC03_CPU_38 > @@ -105,3 +104,4 @@ WORKAROUND_REPEAT_TLBI > WORKAROUND_SPECULATIVE_AT > WORKAROUND_SPECULATIVE_SSBS > WORKAROUND_SPECULATIVE_UNPRIV_LOAD > +WORKAROUND_BROKEN_AMU_CONSTCNT > -- > 2.53.0 >