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Tue, 04 Feb 2025 17:11:35 +0000 Date: Tue, 04 Feb 2025 17:11:33 +0000 Message-ID: <8634gtvdmi.wl-maz@kernel.org> From: Marc Zyngier To: Sebastian Ott Cc: Shameer Kolothum , kvmarm@lists.linux.dev, oliver.upton@linux.dev, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, Cornelia Huck , eric.auger@redhat.com, yuzenghui@huawei.com, wangzhou1@hisilicon.com, jiangkunkun@huawei.com, jonathan.cameron@huawei.com, anthony.jebson@huawei.com, linux-arm-kernel@lists.infradead.org, linuxarm@huawei.com Subject: Re: [PATCH v5 0/4] KVM: arm64: Errata management for VM Live migration In-Reply-To: <76172c57-aac6-d540-5b98-8de100c0886c@redhat.com> References: <20250124151732.6072-1-shameerali.kolothum.thodi@huawei.com> <76172c57-aac6-d540-5b98-8de100c0886c@redhat.com> 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: sebott@redhat.com, shameerali.kolothum.thodi@huawei.com, kvmarm@lists.linux.dev, oliver.upton@linux.dev, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, cohuck@redhat.com, eric.auger@redhat.com, yuzenghui@huawei.com, wangzhou1@hisilicon.com, jiangkunkun@huawei.com, jonathan.cameron@huawei.com, anthony.jebson@huawei.com, linux-arm-kernel@lists.infradead.org, linuxarm@huawei.com 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-20250204_091138_505216_C1AB7949 X-CRM114-Status: GOOD ( 17.69 ) 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 Tue, 04 Feb 2025 16:45:38 +0000, Sebastian Ott wrote: > > Hey, > > On Fri, 24 Jan 2025, Shameer Kolothum wrote: > > On ARM64 platforms most of the errata workarounds are based on CPU > > MIDR/REVIDR values and a number of these workarounds need to be > > implemented by the Guest kernel as well. This creates a problem when > > Guest needs to be migrated to a platform that differs in these > > MIDR/REVIDR values even if the VMM can come up with a common minimum > > feature list for the Guest using the recently introduced "Writable > > ID registers" support. > > Currently MIDR/REVIDR are still RO and guest access is not trapped - so > even with the errata management patches in place the guest state would > change and a migration (between hosts that differ in these regs) would > not be possible. Are there any plans to allow to actually change these? Sure thing. We only need a victim! :) M. -- Without deviation from the norm, progress is not possible.