From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C3BDC20C494 for ; Tue, 4 Feb 2025 17:11:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738689097; cv=none; b=QYCOEWUZUssXnqvFEnagrTowvC8sHzVWprbSVvaRdPWMpKJvbEG6tYSaKvKrg3lbavYeQJKSOqK9+pT4upnqD0sLbsgmwQrFWSjgrLoE10KhLcKeujDLJFgbTKu6D3Sg6I+mby8BYnqZxFmXx5Swj+mT09KIefiQ8/vUeAaeIqk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738689097; c=relaxed/simple; bh=hrbC47N02DT87DswOvF6MjKDFNee3DLRVLKFdueteLo=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=isQKe5+ZfiPPXGefqtPdDYdmbZpyBEywonLco+UbmMzCW4+382uyxHKwQmtOmQTBp9J8m/9Ky0LsBo1Ig47ArAsb/Nzzz10Lt1I1U/D4hexZcTjysmej8eLPIJAl8VG5rXKWAxJx9HRqWKBPTSS6nUyl2lBRr362IzeGpJ+G95o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=o1gR2hi7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="o1gR2hi7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B98AC4CEDF; Tue, 4 Feb 2025 17:11:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738689097; bh=hrbC47N02DT87DswOvF6MjKDFNee3DLRVLKFdueteLo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=o1gR2hi7pyahKqW0F8jO5l32TXBlkXh5RtT/2vpzv7IfqzwOeyJOm/9emiER8yKqv d5jL/jHvMeC1+C0HOOHWw1c6+2KTPv6C/COo1GtzXYO1CbEaKNRpQv0nq8/e00PYVt 5tXQAal4TWB35W63wAwoYFTUELsCFoCRq7Ww46twJoF/FbwJ9OCzV0l7smyOazhxxc G3Z5vqs/0PXXZVY+Hr1EmYBdhv1UMJTYdTfrKyH6K8y3Pm6LPF+3CobdKdvpIwB6XT PTbqVm+mnTDjjegYs3uOGesjSSWI09+rzxgM+eE+mdH16O+1hXQrJoifTdIgTzAVL6 Q1JU/FSiEMjPg== 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 4.95) (envelope-from ) id 1tfMSU-000Uzb-VQ; 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) Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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 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.