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 842C6E77188 for ; Tue, 17 Dec 2024 10:42:29 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From: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=xSu6zANRT/wpbGQaB8aTXezDvtDfr2WBbbVTU125xbM=; b=SAKVD85Iua9eW+/JAEa2GKuAql mpK5GHwmjj0PXc9qcIe+ssfY4ar3xmOTgedP6dJJvR0kt+/9FqB3tm2zgGuLMKC2DZak14NQWgTsk UMIHs3wIBI1rLAdf+6gg35oIauro3sGfHVQ+bi9+nLuMUnhKcYpWzyJIUOPxO8jCqvXR8r38LJnyH pJFX4F4O2+PyxjhIOSOcmJVewQVcmOlQcbXlJmeTtGy4ZxZ60A+/+P2mjcSnk8B3Z8mUo79NQ4byJ 0+aRKS7wxZ0Fy05pG/ZB/fQxXWK0ElasbBfu4/Ml4FPj1KMIVpeinTYN7fj64Z+LntprMh6/uesVy SNQsdwNA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tNV1v-0000000D9bw-0iKj; Tue, 17 Dec 2024 10:42:19 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tNV0l-0000000D9Ou-40Wx for linux-arm-kernel@lists.infradead.org; Tue, 17 Dec 2024 10:41:12 +0000 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 608111007; Tue, 17 Dec 2024 02:41:33 -0800 (PST) Received: from e124191.cambridge.arm.com (e124191.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7FD993F528; Tue, 17 Dec 2024 02:41:03 -0800 (PST) Date: Tue, 17 Dec 2024 10:40:58 +0000 From: Joey Gouly To: Greg KH Cc: stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, gshan@redhat.com, james.morse@arm.com, maz@kernel.org, oliver.upton@linux.dev, shameerali.kolothum.thodi@huawei.com, vt@altlinux.org, Suzuki K Poulose , Zenghui Yu , Jing Zhang , Catalin Marinas , Will Deacon Subject: Re: [PATCH 6.6 v1] KVM: arm64: Disable MPAM visibility by default and ignore VMM writes Message-ID: <20241217104058.GA2151333@e124191.cambridge.arm.com> References: <20241212151406.1436382-1-joey.gouly@arm.com> <2024121528-refurbish-plausibly-31c7@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2024121528-refurbish-plausibly-31c7@gregkh> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241217_024108_047528_4645CF4B X-CRM114-Status: GOOD ( 24.01 ) 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 Sun, Dec 15, 2024 at 10:22:53AM +0100, Greg KH wrote: > On Thu, Dec 12, 2024 at 03:14:06PM +0000, Joey Gouly wrote: > > From: James Morse > > > > commit 6685f5d572c22e1003e7c0d089afe1c64340ab1f upstream. > > > > commit 011e5f5bf529f ("arm64/cpufeature: Add remaining feature bits in > > ID_AA64PFR0 register") exposed the MPAM field of AA64PFR0_EL1 to guests, > > but didn't add trap handling. A previous patch supplied the missing trap > > handling. > > > > Existing VMs that have the MPAM field of ID_AA64PFR0_EL1 set need to > > be migratable, but there is little point enabling the MPAM CPU > > interface on new VMs until there is something a guest can do with it. > > > > Clear the MPAM field from the guest's ID_AA64PFR0_EL1 and on hardware > > that supports MPAM, politely ignore the VMMs attempts to set this bit. > > > > Guests exposed to this bug have the sanitised value of the MPAM field, > > so only the correct value needs to be ignored. This means the field > > can continue to be used to block migration to incompatible hardware > > (between MPAM=1 and MPAM=5), and the VMM can't rely on the field > > being ignored. > > > > Signed-off-by: James Morse > > Co-developed-by: Joey Gouly > > Signed-off-by: Joey Gouly > > Reviewed-by: Gavin Shan > > Tested-by: Shameer Kolothum > > Reviewed-by: Marc Zyngier > > Link: https://lore.kernel.org/r/20241030160317.2528209-7-joey.gouly@arm.com > > Signed-off-by: Oliver Upton > > [ joey: fixed up merge conflict, no ID_FILTERED macro in 6.6 ] > > Signed-off-by: Joey Gouly > > Cc: stable@vger.kernel.org # 6.6.x > > Cc: Vitaly Chikunov > > Link: https://lore.kernel.org/linux-arm-kernel/20241202045830.e4yy3nkvxtzaybxk@altlinux.org/ > > --- > > > > This fixes an issue seen when using KVM with a 6.6 host kernel, and > > newer (6.13+) kernels in the guest. > > > > Tested with a stripped down version of set_id_regs from the original > > patch series. > > What about 6.12.y? You can't just skip a stable tree, otherwise you > will get a regression when you upgrade to 6.12.y, right? I did have it ported/tested locally, but I wasn't sure of the stable process, so just sent out one! Next time I will send all the backports at the same time. Thanks Marc Z for sending it out! Joey