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Tsirkin" , qemu-devel@nongnu.org Subject: Re: [PULL 9/9] hw/i386: pass RNG seed via setup_data entry Date: Thu, 04 Aug 2022 17:56:09 +0100 In-reply-to: Message-ID: <87bkt0nduu.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::32c; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32c.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, T_SCC_BODY_TEXT_LINE=-0.01 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" Daniel P. Berrang=C3=A9 writes: > On Thu, Jul 21, 2022 at 06:36:21PM +0200, Paolo Bonzini wrote: >> From: "Jason A. Donenfeld" >>=20 >> Tiny machines optimized for fast boot time generally don't use EFI, >> which means a random seed has to be supplied some other way. For this >> purpose, Linux (=C3=A2=E2=80=B0=C2=A55.20) supports passing a seed in th= e setup_data table >> with SETUP_RNG_SEED, specially intended for hypervisors, kexec, and >> specialized bootloaders. The linked commit shows the upstream kernel >> implementation. >>=20 >> At Paolo's request, we don't pass these to versioned machine types =C3= =A2=E2=80=B0=C2=A47.0. > > > This change has also broken direct kernel measured boot with AMD SEV > confidential virtualization. FWIW this is why we had to introduce the dtb-randomness control knob for ARM -M virt machines. Although we have deprecated the old dtb-kaslr-seed knob and it has always enabled by default because the measured boot was sufficiently new the few people working with it could just add it to their command lines. --=20 Alex Benn=C3=A9e