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Fri, 04 Apr 2025 16:01:19 -0700 (PDT) Received: from [192.168.122.15] ([173.164.107.234]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-229785ad9a0sm38250265ad.39.2025.04.04.16.01.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Apr 2025 16:01:19 -0700 (PDT) Message-ID: Date: Fri, 4 Apr 2025 16:01:16 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] hw/riscv/virt.c: change default CPU to 'max' To: qemu-devel@nongnu.org References: <20250404152750.332791-1-dbarboza@ventanamicro.com> <20250404152750.332791-3-dbarboza@ventanamicro.com> Content-Language: en-US From: Richard Henderson In-Reply-To: <20250404152750.332791-3-dbarboza@ventanamicro.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::42e; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42e.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 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. r~