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 3602BCFD340 for ; Mon, 24 Nov 2025 17:48:01 +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:Content-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID: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=iQUnZbuG1svCUowAEqMGR4TxP2j1lmCn1gxvlSGQyoM=; b=cPLlFDhEs+IQGjzrn00SN7Hlor P7+w/dW9M0kszKxHKJZW04caId+YmiU9UZT5GajQhXjWlTUnuQCJOgvLsdVdma0v85CoHKK0JOXnz Iu00L/Cm3KWoXZmFGflzvqPALyyAHrmXRgTjeQiK7dJ21sBzDFDvuMr7MfkRcC37fwiktQCCDLkPy TwHqt3+9WGP7Qvjnc8+FL6HfSLmUB5HbsaBTYszDwLaVpsV56M5wpz7Z7fvOXYN6HwqQeiBjqvUhv HIiMIlitd8Y51jLA+Jf6yaofxvJ3q6V3X1snMXiDjZht7tHxwlrNIaQAP+U7i9noUxj/MJLuDWXpu p4qwCBdQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNafO-0000000C80T-0tMU; Mon, 24 Nov 2025 17:47:58 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNafM-0000000C80F-49cB for linux-arm-kernel@lists.infradead.org; Mon, 24 Nov 2025 17:47:57 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 24F3D6016B; Mon, 24 Nov 2025 17:47:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0FA6C116C6; Mon, 24 Nov 2025 17:47:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764006475; bh=u9LC0QOwKIPGbGzJvcRIjbKTr5QDS5OcptRArSq5Rbk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Oa39+khr+k7qNyexcw/Yh5q/y8sX0e6so7K39AWgPDLw7Ju0zEZdfzcYXGAVEowU0 t2Eg6aWfbDAxYGEUvFzs5JUEa+u4ukSkyVoidlT6gN3qId+2I0tnLACIzlV10Otlj8 9hTeG/lOEVuKcTgU4lhgY3een7CP9cWPcoh+/DhLmtPAV1pQmzahMlXhpim9biqU0U mIy7bmkHYi16snt3SBxs8Ro3JG48gnvCOuPjev9DS5piVgHiFn+mIsE7WLio3pSG8t TK8wUvwgh/I9gtyqpcUGjbGrRiRV7LzGIDWpYAyjG+1IKai3qF87g9/x9MnOiwu7D/ F/ZXwRRf7vOVA== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1vNafJ-00000007vfW-1mz0; Mon, 24 Nov 2025 17:47:53 +0000 Date: Mon, 24 Nov 2025 17:47:53 +0000 Message-ID: <86ikezqq46.wl-maz@kernel.org> From: Marc Zyngier To: Vladimir Zapolskiy Cc: Catalin Marinas , Will Deacon , Mark Brown , linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH] arm64: cpufeature: Unrestrict ID_AA64MMFR1_EL1 bit assignments In-Reply-To: <20251124162955.3616314-1-vladimir.zapolskiy@linaro.org> References: <20251124162955.3616314-1-vladimir.zapolskiy@linaro.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: vladimir.zapolskiy@linaro.org, catalin.marinas@arm.com, will@kernel.org, broonie@kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false 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, 24 Nov 2025 16:29:55 +0000, Vladimir Zapolskiy wrote: > > It appears that 4 out of 8 Qualcomm SM8450 SoC cores do not generate > an SError interrupt due to an External abort on a speculative read, > and it is reported as a failed sanity check on boot: > > CPU features: SANITY CHECK: Unexpected variation in SYS_ID_AA64MMFR1_EL1. Boot CPU: 0x00000011212122, CPU4: 0x00000010212122 > CPU features: SANITY CHECK: Unexpected variation in SYS_ID_AA64MMFR1_EL1. Boot CPU: 0x00000011212122, CPU5: 0x0000001021212 > CPU features: SANITY CHECK: Unexpected variation in SYS_ID_AA64MMFR1_EL1. Boot CPU: 0x00000011212122, CPU6: 0x00000010212122 > CPU features: SANITY CHECK: Unexpected variation in SYS_ID_AA64MMFR1_EL1. Boot CPU: 0x00000011212122, CPU7: 0x00000010212122 > > Due to the failed sanity check the kernel is marked as tainted in runtime: > > Tainted: [S]=CPU_OUT_OF_SPEC > > Unrestrict the ID_AA64MMFR1_EL1 SpecSEI bits, since apparently it's > a supported option at least on this heterogeneous SoC. Supporting asymmetric configurations has always been on the basis of having the same feature set. Just because some SoCs ignore this requirement doesn't make it acceptable. Tainting the kernel is the right thing to do IMO, because that's an unexpected difference. Additionally, making things non-strict may open a gaping hole in the virtualisation support. All you would need to do is boot on the CPUs that do not have SpecSEI, and bring up the CPUs that do have SpecSEI late, *after* you have started a VM. That VM will have been told that it cannot get a speculative SError, and yet will be able to run on CPUs that do. Thanks, M. -- Without deviation from the norm, progress is not possible.