From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 71BFC33ADBF for ; Thu, 17 Sep 2026 05:56:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789624606; cv=none; b=Pz5wwjRLTFDAZr7N2N8fDpafWyoS1uWq2moVsgVNxS4DaZboPa/nBHn5KmxWm5zqGyMqQ/i1kngCg/iz7M9lldP8lpLOK9N3WN8VKKokaAJt1PoJVyKdbfgsWohlGthslA/dGXbMEKFBaCqnNrDybGG07H1EVSK1Htix/tTkDg0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789624606; c=relaxed/simple; bh=IRwy3v4RbeEQb7tDTKXoI8cnAJR4oVGR+vCDRpGGxF0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ahA0m8HcZ4F5Kaii1tLP/CvFkoiRn8FypW71gnak7CwMaU5mCHcUkD3XGV5MgRdzOeKFS1wA2g9rX/kXqW6HR8A7C5gpMMIpTPWNLEO8tQDjPodwm593RgeR4Ai6KaIrqC7yvX1g6YghoKSE8p0QvMsLQzwojnWPMzLwaIGzTQc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=MNpbfkV9; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=Cx3pGQJk; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MNpbfkV9"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="Cx3pGQJk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1789624603; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a5IexDE5RwVjuRt7QVn2TA0PVUO278ucUqo3lGJjXXA=; b=MNpbfkV9rcuZoJyvzbeGrnMwU+4p3svFlwF/SaXuh/x0ofE1rtl7jpF8rhnSu2eO2f5YUZ +ioa/vRrGxZ3s11Su7myEwPlwdXl1EiKSDx0qhHWwuJ2fgZIDxldTHwYvE9cXnj1KrVajY JhCWVCJmOll1SHE2UYb6AVztIt0JYOc= Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-539-tQEIuf7iO2WD4lqwaJUiLQ-1; Thu, 17 Sep 2026 01:56:36 -0400 X-MC-Unique: tQEIuf7iO2WD4lqwaJUiLQ-1 X-Mimecast-MFC-AGG-ID: tQEIuf7iO2WD4lqwaJUiLQ_1789624591 Received: by mail-pf1-f199.google.com with SMTP id d2e1a72fcca58-86a6f4ba619so584381b3a.1 for ; Wed, 16 Sep 2026 22:56:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1789624591; x=1790229391; darn=vger.kernel.org; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to :content-type; bh=a5IexDE5RwVjuRt7QVn2TA0PVUO278ucUqo3lGJjXXA=; b=Cx3pGQJkdGIa0WKNWPCo9W40OW6agjBtqMbLXozguwAQOZ09O0lmRIyVSdEDlNHL61 ZM8vYafka1jfEe9RU8lAlpW6X5zs4fhBkFKT+B1r3RWI2buvR7kugGta6SodmOPn+b30 zgktbNNNPcN5Y41EL1l9jxilkITlDseD+tCcwxICKsVCiLvMxgmKESPFMi0uPwpHCkad GjE0DLNr996/spZQUAA+eWZrA4uUhvU2oaW0/JAVafkGhew2plOmrivnz2g0+9i4dHEt mgaXsLuqLcnCw4vlkkLzhoZMuriyTFgfbkb64yeUIG2PRP7uDgre8DdBHnpv2I8g16/A Nn2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789624591; x=1790229391; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=a5IexDE5RwVjuRt7QVn2TA0PVUO278ucUqo3lGJjXXA=; b=tGjth647eCWEhFWCgmSMAcAIG2m8UyBBhYlrMHz6JoHT9rMke8mFMZL0dmFZMTgUdI U9WsZHGQuK7PVzSf38L6zpZNRSFVlyadJucQ34ALvNBajeLC5/B/Qi8ihRD5+6iASRFj EX4/oJ1zZKWUYFT0aPKIoPAICZuk+7UH2WdMUn4Q5cFJAF/qo6HrboBCtILpUNnllt+E KlP9/F0zY38E6kg77dOZfjkGnDn5KHzUAuHQsKPbnaE+lsX62rLhhwdNWp82ROzRvOmv ZF9p6XGsn47BWpVnesR4Xh1n5IkdyrX09xqtOEVwLUlOiFcO6FN1IpkEvNQeeY/Gc2jQ pE2A== X-Forwarded-Encrypted: i=1; AKwUvBz4e48dZPyxMynD1PsUBZmq6Q1QtwfHJ+MEEmhHHSMFeNngQGV0MnzFe4cWEZ0QaQtAeLw2G3Wu6UPMHpE=@vger.kernel.org X-Gm-Message-State: AFuF++kiZQpREGbRoscEuXgKSkjTzenwAwdblZDkG/cbFbjE5zbB49tL 1raw+wYNtocusE7HZLsXh4jwCdinNeE+NGaH3ERXbghcLXLXh2hRi66Zwms/qgLybwb4nL162q8 3dXysoa1czlnETBvT45WrLnj8AaRo5zMPxl4o/lRSfXB+cZlFZSVQIWl20ug60rGntg== X-Gm-Gg: AYBFou3YJau5WQpBbe1Q/f5Z76h20iBcMFkF/6ZaeAL7np1T48DpWTAP6b/JQDsctob d2UlLj8dQPJilIVi8ZHjM2p/wKKZyXf/fDEnm37sGAD0EtVrwBr5gfz/ytZzZ+XgusWjUPrZ9BF C57VKC9FEnpYQ+2P24RxQ1NjAJc/NndtxHm8+hTLi0oNaQOKzHm9pBRkXQmjbdkccN7TjiKR9LG ybH4o3Dul8q9/WTQsy3Pf8DQNP28ibgs7pDQhKvwZUU4jGx6FzZgJY+8Q/GjJ7iMIQgXAjpHL9D Dcain916pTsrDU4f4jZk/A/bEK2exRTwzVlrjXWhIijioOUoR24PgiCK+HY4kCy8B0dxMGGNI2B vyZRQiwNWqnzn3HxaiVgS0AAUIKjG6Qr7GKbBGol1zw== X-Received: by 2002:a05:6a00:bd0e:b0:845:ba94:a56 with SMTP id d2e1a72fcca58-872372c313emr11817049b3a.5.1789624590918; Wed, 16 Sep 2026 22:56:30 -0700 (PDT) X-Received: by 2002:a05:6a00:bd0e:b0:845:ba94:a56 with SMTP id d2e1a72fcca58-872372c313emr11816999b3a.5.1789624590365; Wed, 16 Sep 2026 22:56:30 -0700 (PDT) Received: from [192.168.68.52] (n175-34-8-244.mrk21.qld.optusnet.com.au. [175.34.8.244]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-871febde2f7sm2262500b3a.6.2026.09.16.22.56.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Sep 2026 22:56:29 -0700 (PDT) Message-ID: Date: Thu, 17 Sep 2026 15:56:24 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm_mpam: resctrl: Catch and propagate error from get_cpu_cacheinfo_id() To: Andre Przywara , Ben Horgan , James Morse Cc: Reinette Chatre , Fenghua Yu , Tony Luck , Dave Martin , Yin Li , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260902143757.3469690-1-andre.przywara@arm.com> <2c682691-3037-4d62-a941-bc41baca35aa@arm.com> <4f35abf6-6dac-4c60-9ece-c1af02a98c9c@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <4f35abf6-6dac-4c60-9ece-c1af02a98c9c@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/16/26 11:34 PM, Andre Przywara wrote: > On 9/16/26 11:49, Ben Horgan wrote: >> On 07/09/2026 13:59, Ben Horgan wrote: >>> On 02/09/2026 15:37, Andre Przywara wrote: >>>> get_cpu_cacheinfo_id() can fail, in which case it returns a negative >>>> error value. >>>> >>>> Check the returned value for this error condition, before passing the >>>> value on to other code, which would hide the negative number in some high >>>> value in the unsigned type. >>>> >>>> Fixes: 36528c7681b8 ("arm_mpam: resctrl: Add support for 'MB' resource") >>>> Signed-off-by: Andre Przywara >>> >>> This looks good to me. Out of interest what led you to find this? >>> >>> Reviewed-by: Ben Horgan >> >> I seem to have been a bit hasty here. >> >> Sashiko points out at [1] that 0xFFFFFFFF is the only value we were previously considering invalid >> and that the value coming from dt or acpi can provid other valid values that would after this patch >> be considered invalid. > > Fair, and I can easily change the check to only check explicitly for -1. > > But this is somewhat broken already, right? I mean the return type for the existing get_cpu_cacheinfo_id() has always been "int". It looks like this comes from the x86 world, where the cache IDs never get that large? I can have a deeper look, but my gut feeling is that this is practically irrelevant, since we barely see Aff3 at all, not to mention high values of it. > I guess we also can exploit CACHE_ID flag in struct cacheinfo::attributes. struct cacheinfo::id is valid only when CACHE_ID flag is set. So we would introduce our own helper as below, where an extra return value to indicate the (returned) cached ID is valid or not. In drivers/resctrl/mpam_internal.h: /* NULL is returned if struct cacheinfo::attributes don't have CACHE_ID set */ static inline bool mpam_cpu_cache_id(int cpu, int level, unsigned int *id) { struct cacheinfo *ci = get_cpu_cacheinfo_level(cpu, level); if (!ci) return false; if (id) *id = ci->id; return true; } Thanks, Gavin