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[88.21.201.17]) by smtp.gmail.com with ESMTPSA id i16sm4014251wmq.3.2021.03.18.02.47.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Mar 2021 02:47:43 -0700 (PDT) Subject: Re: [PATCH v2 3/3] target/arm: Restrict v7A TCG cpus to TCG accel To: qemu-devel@nongnu.org, Peter Maydell , "Dr. David Alan Gilbert" References: <20210221222617.2579610-1-f4bug@amsat.org> <20210221222617.2579610-4-f4bug@amsat.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <8a302c84-b69c-b0c2-de45-607dd1f686a6@redhat.com> Date: Thu, 18 Mar 2021 10:47:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Jones , qemu-arm@nongnu.org, =?UTF-8?Q?Alex_Benn=c3=a9e?= , Claudio Fontana Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On 3/11/21 11:43 AM, Claudio Fontana wrote: > On 2/21/21 11:26 PM, Philippe Mathieu-Daudé wrote: >> KVM requires the target cpu to be at least ARMv8 architecture >> (support on ARMv7 has been dropped in commit 82bf7ae84ce: >> "target/arm: Remove KVM support for 32-bit Arm hosts"). >> >> A KVM-only build won't be able to run TCG cpus, move the >> v7A CPU definitions to cpu_tcg.c. >> >> Reported-by: Peter Maydell >> Reviewed-by: Peter Maydell >> Signed-off-by: Philippe Mathieu-Daudé > > > Here I think it's better to keep the "a15" cpu around, > until we fix the board configuration situation. > > I added a patch that does that into my KVM-only build series, to avoid the resulting breakages. Actually I got a downstream report that this break migration from QEMU 5.2 to QEMU 6.0. I first thought it was on an old kernel (with 32-bit KVM enabled), but not, it is for Aarch64 VMs on recent KVM (without 32-bit support) but the 'virt' machines were started with default Cortex-A15 CPU... mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15"); I'm not sure upstream should care about this case, but I though maybe you could give me hints about the best way to keep old VMs working, as this likely affects any distribution. Obviously not upgrading QEMU is not a solution :) The simplest seems to revert 82bf7ae84ce and this patch, but I doubt this will be enough. Maybe there is some clever thing to do before reverting 82bf7ae84ce, that could also benefit upstream, by doing something with versioned machines? I have no idea (yet) how that work and if it could work. Thanks, Phil.