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[213.99.162.212]) by smtp.gmail.com with ESMTPSA id a7sm6636928wrr.89.2019.11.08.06.52.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Nov 2019 06:52:14 -0800 (PST) Subject: Re: [PATCH v4 1/1] arm64: Implement archrandom.h for ARMv8.5-RNG To: Ard Biesheuvel , Marc Zyngier References: <20191106141954.30657-1-rth@twiddle.net> <20191106141954.30657-2-rth@twiddle.net> <23ce309b-1561-ed95-7ce7-463a991bd19b@linaro.org> From: Richard Henderson Openpgp: preference=signencrypt Message-ID: Date: Fri, 8 Nov 2019 15:52:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191108_065216_235256_6F808FD4 X-CRM114-Status: GOOD ( 13.77 ) 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 , "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , 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 11/8/19 3:24 PM, Ard Biesheuvel wrote: >>> To add_interrupt_randomness(), invoked by handle_irq_event_percpu(). >>> Better if I reword the above to include the function name? >>> >> >> This is one of the several places where arch_random_get_seed_long() is >> called, so if you are going to single it out like that, it does make >> sense to clarify that. >> > > Looking more carefully at that code, it seems we call > arch_get_random_seed_long() NR_CPUS times per second, and assuming > that our RNDRRS sysreg will be reseeded from a resource that is shared > between all the cores, I am now wondering if this is such a good fit > after all, especially in the context of virtualization and > accessibility of both sysregs all the way down to EL0. > > I propose we go with RNDR instead, at least for the time being, and > once actual hardware appears, we can try to figure out how these > pieces best fit together. This is what I started with, based on the powerpc implementation. I can certainly revert to that easily. r~ _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel