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Mon, 16 Dec 2024 08:51:38 +0000 Date: Mon, 16 Dec 2024 08:51:38 +0000 Message-ID: <86a5cwrox1.wl-maz@kernel.org> From: Marc Zyngier To: Greg KH Cc: Joey Gouly , stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, gshan@redhat.com, james.morse@arm.com, 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 In-Reply-To: <2024121528-refurbish-plausibly-31c7@gregkh> References: <20241212151406.1436382-1-joey.gouly@arm.com> <2024121528-refurbish-plausibly-31c7@gregkh> 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/29.4 (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: gregkh@linuxfoundation.org, joey.gouly@arm.com, stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, gshan@redhat.com, james.morse@arm.com, oliver.upton@linux.dev, shameerali.kolothum.thodi@huawei.com, vt@altlinux.org, suzuki.poulose@arm.com, yuzenghui@huawei.com, jingzhangos@google.com, catalin.marinas@arm.com, will@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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241216_005142_361520_4E4ADD64 X-CRM114-Status: GOOD ( 25.90 ) 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, 15 Dec 2024 09:22:53 +0000, 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? Posted as [1]. M. [1] https://lore.kernel.org/r/20241216085002.334880-1-maz@kernel.org -- Without deviation from the norm, progress is not possible.