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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4409d2b77f9sm14328295e9.25.2025.04.24.03.00.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Apr 2025 03:00:58 -0700 (PDT) Message-ID: <9d2816f1-c4e1-4da0-bcb7-fd2c4f4adec4@linaro.org> Date: Thu, 24 Apr 2025 12:00:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] hw/riscv/virt.c: change default CPU to 'max' To: Alistair Francis , Richard Henderson Cc: qemu-devel@nongnu.org References: <20250404152750.332791-1-dbarboza@ventanamicro.com> <20250404152750.332791-3-dbarboza@ventanamicro.com> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::42a; envelope-from=philmd@linaro.org; helo=mail-wr1-x42a.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 7/4/25 01:31, Alistair Francis wrote: > On Sat, Apr 5, 2025 at 9:02 AM Richard Henderson > wrote: >> >> On 4/4/25 08:27, Daniel Henrique Barboza wrote: >>> Using 'max' as >>> default CPU is done by other QEMU archs like aarch64 so we'll be more >>> compatible with everyone else. >> >> This isn't true. qemu-system-aarch64 -M virt defaults to cortex-a15 (for hysterical >> raisins), which is completely and totally useless. Which means that one must always pass >> a -cpu option to qemu-system-aarch64. >> >> Moreover, -cpu max has zero migration guarantees, so anyone who wants to be able to >> reliably migrate is encouraged to use a real cpu model. >> >> I suppose, for throwaway VMs, -cpu max is a decent default. But there's a lot to be said >> for not specifying a default at all. > > I agree. If we aren't going to specify a default machine, why specify > a default CPU? > > It probably makes sense to deprecate the default CPU for non-vendor > machines and then force users to pick their own CPU. That should start > in 10.1 so it's a release offset from the removal of the default > machine. IMHO this is the sanest things to do. > Then maybe think about even removing rv32/rv64 CPUs and push people to > the profiles, as it's a lot clearer what they are getting. > > Alistair > >> >> >> r~ >> >