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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2NioKeZtBMGmQq42dQ7mU02YW1pmqEsr7pSup03whQg=; b=hpQI+ue5Wrxk4d1EWT+r4Jjv+hBSuvevtYNTd0jgwnn9k+pezCHnyBTJxciDZThtsX ixIkh+hIMB1uOxWHkGgP2HEu2ylpwdMtTNg4wzWpW3iu3evEZ2MqRmyMkZvFFpUTALD7 OmBD6/BKuBEQvJbxuNFr5ZGSWw8oG8jAdxYiSZc+ITVwtDbTQUsEFbqTq31dogF2bHYJ aZP1UPFYvCTtStC5cHfKLSrnRnaQXCfxyW8Uq1CK4WCb38ehZ7tfpJRg9syP0fjGtBpt 0uEmADC8vTWjAcyUbFxDb+nk/q6U6aMgVtAXilaLAZcGzBYFAEopvceb8B/PqhKXf7as r9kg== X-Gm-Message-State: APjAAAUdmiCTtG1n9U2j7YghC8yYEpTyq75QGrG9NexrSP7l/9XSEzyr MJ+0l+QwsPjP/+2uWjKMEn9VcA5JCM3QoPGOB0vJmQ== X-Google-Smtp-Source: APXvYqwkavqLZfkeI2+PDVkGXlezN0UmcqWgb0g+qWdK44o8R6jH+9Jwige1+nSB1O4bIv7BEiqY+nC0WGRt1KL+i9Y= X-Received: by 2002:a1c:3dc3:: with SMTP id k186mr31385654wma.95.1579080134926; Wed, 15 Jan 2020 01:22:14 -0800 (PST) MIME-Version: 1.0 References: <20200110122341.8445-1-broonie@kernel.org> <20200110122341.8445-3-broonie@kernel.org> <20200115091615.GA21692@willie-the-truck> In-Reply-To: <20200115091615.GA21692@willie-the-truck> From: Ard Biesheuvel Date: Wed, 15 Jan 2020 10:22:03 +0100 Message-ID: Subject: Re: [PATCH v10 2/3] arm64: random: Add data to pool from setup_arch() To: Will Deacon X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200115_012217_114985_D7CEE7B7 X-CRM114-Status: GOOD ( 22.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Catalin Marinas , Mark Brown , Richard Henderson , linux-arm-kernel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 15 Jan 2020 at 10:16, Will Deacon wrote: > > On Wed, Jan 15, 2020 at 08:48:46AM +0100, Ard Biesheuvel wrote: > > On Fri, 10 Jan 2020 at 13:23, Mark Brown wrote: > > > > > > Since the arm64 ARCH_RANDOM implementation is not available until > > > cpufeature has determined the system capabilities it can't be used by > > > the generic random code to initialize the entropy pool for early use. > > > Instead explicitly add some data to the pool from setup_arch() if the > > > boot CPU supports v8.5-RNG, this is the point recommended by the generic > > > code. > > > > > > Note that we are only adding data here, it will be mixed into the pool > > > but won't be credited as entropy. There are currently no suitable > > > interfaces for that at present - extending the random code to provide > > > those will be done as a future step. Providing data is better than not > > > doing so as it will still provide an increase in variation in the output > > > from the random code and there will be no impact on the rate at which > > > entropy is credited compared to what we have without this patch. > > > > > > > This is slightly unfortunate, as this way, we lose the ability to use > > random.trust_cpu=1 to get the entropy credited and initialize CRNG > > early. > > Agreed. Do you think we should wait for that support before merging the > series? Given that I don't know of any CPUs implementing this extension, > we can probably afford not to rush this in. > In a previous iteration, we did have a functional arch_get_random_seed_long() early on, which would solve this issue without even needing a patch like this. Perhaps Mark (Rutland) can give a recap of his concerns at the time? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel