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([2001:b07:6468:f312:9af8:e5f5:7516:fa89]) by smtp.googlemail.com with ESMTPSA id b25-20020a17090630d900b00722fadc4279sm819518ejb.124.2022.07.21.05.41.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Jul 2022 05:41:52 -0700 (PDT) Message-ID: <8329bd5c-a0aa-5d91-657a-204fb6d789b0@redhat.com> Date: Thu, 21 Jul 2022 14:41:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry Content-Language: en-US To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , "Jason A. Donenfeld" Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Marcel Apfelbaum , Richard Henderson , Eduardo Habkost , Peter Maydell , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Laurent Vivier References: <20220721104730.434017-1-Jason@zx2c4.com> <20220721104950.434544-1-Jason@zx2c4.com> <20220721065744-mutt-send-email-mst@kernel.org> <1ee57e75-94a1-cf75-7d49-0d399607fee9@redhat.com> From: Paolo Bonzini 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::52e; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x52e.google.com X-Spam_score_int: -14 X-Spam_score: -1.5 X-Spam_bar: - X-Spam_report: (-1.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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" On 7/21/22 14:27, Daniel P. Berrangé wrote: > > Pre-existing guests which have merely upgraded their QEMU instance > won't get the feature, because they'll be fixed on the old machine > type to guarantee no guest ABI change. This isn't a problem, as > such pre-existing guests likely won't have the new Linux code to > consume the seed anyway. In fact this isn't a given either and depends on how these pre-existing guests are managed. People that do not use Libvirt, or that just start their guests with "virsh create" and some on-disk XML file, _will_ get the new feature. The way QEMU does things is that fw_cfg is part of guest ABI, and this is _not_ up for discussion. You're not the first one to be confused[1] and you probably will not be the last, so this means that the whole concept of guest ABI should be documented better. (By the way, even though I agree that the failure is completely theoretical apart from the record-replay case, it can actually be reproduced easily by sticking a long-enough sleep in pc-bios/optionrom/linuxboot_dma.c). Paolo