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 9780137A486 for ; Fri, 16 Jan 2026 11:57:32 +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=1768564653; cv=none; b=HcCcIXSoEzwfJkwsLYzE0fXPuGPVmveUKJij7xp0zHafl+5kxe5gza06kItdVl2zpgJbBxaVVptjD+poe7EttBAilkVsjvVgraBOPXup+RoajnYcQzu+eUhPn8Dc0rbDNXBBT6YExdLzOTtIRRFBjPEUErFYFavZmVrV8PPI6v8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768564653; c=relaxed/simple; bh=SKnRf9JLyc8Pd7m/TOJfHbLxu6+wxbvNwtz00TcKeE8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JgRYoPnyir+VUBtsfmnsYUJrukgnTdFQ+Q2G3sSH5NIxca4zPLkYoBqhEaW+ARuxs/vMBALME/uXR9BIXYcuzi76Tn+Y6JPYw9ohoXu+BR6zeLyQmAcdy0ZWNeHBYq0DTsUE/cD9xVHDZqQjRSl6Oa2mWfCVm1VuVnQK/9iDpaA= 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; 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 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 649971515; Fri, 16 Jan 2026 03:57:25 -0800 (PST) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 55D763F694; Fri, 16 Jan 2026 03:57:28 -0800 (PST) Date: Fri, 16 Jan 2026 11:57:25 +0000 From: Catalin Marinas To: Ben Horgan Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, carl@os.amperecomputing.com, dave.martin@arm.com, david@kernel.org, dfustini@baylibre.com, fenghuay@nvidia.com, gshan@redhat.com, james.morse@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peternewman@google.com, punit.agrawal@oss.qualcomm.com, quic_jiles@quicinc.com, reinette.chatre@intel.com, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, tan.shaopeng@fujitsu.com, xhao@linux.alibaba.com, will@kernel.org, corbet@lwn.net, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, kvmarm@lists.linux.dev Subject: Re: [PATCH v3 02/47] arm_mpam: Use non-atomic bitops when modifying feature bitmap Message-ID: References: <20260112165914.4086692-1-ben.horgan@arm.com> <20260112165914.4086692-3-ben.horgan@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260112165914.4086692-3-ben.horgan@arm.com> On Mon, Jan 12, 2026 at 04:58:29PM +0000, Ben Horgan wrote: > In the test__props_mismatch() kunit test we rely on the struct mpam_props > being packed to ensure memcmp doesn't consider packing. Making it packed > reduces the alignment of the features bitmap and so breaks a requirement > for the use of atomics. As we don't rely on the set/clear of these bits > being atomic, just make them non-atomic. > > Reviewed-by: Jonathan Cameron > Signed-off-by: Ben Horgan > --- > Changes since v2: > Add comment (Jonathan) > --- > drivers/resctrl/mpam_internal.h | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h > index 17cdc3080d58..e8971842b124 100644 > --- a/drivers/resctrl/mpam_internal.h > +++ b/drivers/resctrl/mpam_internal.h > @@ -200,8 +200,12 @@ struct mpam_props { > } PACKED_FOR_KUNIT; > > #define mpam_has_feature(_feat, x) test_bit(_feat, (x)->features) > -#define mpam_set_feature(_feat, x) set_bit(_feat, (x)->features) > -#define mpam_clear_feature(_feat, x) clear_bit(_feat, (x)->features) > +/* > + * The non-atomic get/set operations are used because if struct mpam_props is > + * packed, the alignment requirements for atomics aren't met. > + */ > +#define mpam_set_feature(_feat, x) __set_bit(_feat, (x)->features) > +#define mpam_clear_feature(_feat, x) __clear_bit(_feat, (x)->features) After discussing privately, I can see how test__props_mismatch() can end up with unaligned atomics on the mmap_props::features array. Happy to pick it up for 6.19 (probably the first patch as well, though that's harmless). Is there a Fixes tag here for future reference? -- Catalin