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Thu, 05 Nov 2020 14:48:06 +0000 MIME-Version: 1.0 Date: Thu, 05 Nov 2020 14:48:06 +0000 From: Marc Zyngier To: Ard Biesheuvel Subject: Re: [PATCH v2 4/5] arm64: Add support for SMCCC TRNG entropy source In-Reply-To: References: <20201105125656.25259-1-andre.przywara@arm.com> <20201105125656.25259-5-andre.przywara@arm.com> <20201105134142.GA4856@sirena.org.uk> <20201105140322.GH82102@C02TD0UTHF1T.local> <20201105143023.GI82102@C02TD0UTHF1T.local> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <299b7ec794a5f114757078b3eb1bbb8c@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: ardb@kernel.org, mark.rutland@arm.com, broonie@kernel.org, andre.przywara@arm.com, will@kernel.org, catalin.marinas@arm.com, linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, sudeep.holla@arm.com, lorenzo.pieralisi@arm.com, linus.walleij@linaro.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201105_094810_138907_1F7B841C X-CRM114-Status: GOOD ( 19.20 ) 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 , Lorenzo Pieralisi , Andre Przywara , Linus Walleij , Sudeep Holla , Russell King , Linux Kernel Mailing List , Mark Brown , Catalin Marinas , Will Deacon , kvmarm , Linux ARM Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-11-05 14:34, Ard Biesheuvel wrote: > On Thu, 5 Nov 2020 at 15:30, Mark Rutland wrote: >> >> On Thu, Nov 05, 2020 at 03:04:57PM +0100, Ard Biesheuvel wrote: >> > On Thu, 5 Nov 2020 at 15:03, Mark Rutland wrote: >> > > On Thu, Nov 05, 2020 at 01:41:42PM +0000, Mark Brown wrote: >> > > > On Thu, Nov 05, 2020 at 12:56:55PM +0000, Andre Przywara wrote: >> >> > > That said, I'm not sure it's great to plumb this under the >> > > arch_get_random*() interfaces, e.g. given this measn that >> > > add_interrupt_randomness() will end up trapping to the host all the time >> > > when it calls arch_get_random_seed_long(). >> > >> > As it turns out, add_interrupt_randomness() isn't actually used on ARM. >> >> It's certainly called on arm64, per a warning I just hacked in: >> >> [ 1.083802] ------------[ cut here ]------------ >> [ 1.084802] add_interrupt_randomness called >> [ 1.085685] WARNING: CPU: 1 PID: 0 at drivers/char/random.c:1267 >> add_interrupt_randomness+0x2e8/0x318 >> [ 1.087599] Modules linked in: >> [ 1.088258] CPU: 1 PID: 0 Comm: swapper/1 Not tainted >> 5.10.0-rc2-dirty #13 >> [ 1.089672] Hardware name: linux,dummy-virt (DT) >> [ 1.090659] pstate: 60400085 (nZCv daIf +PAN -UAO -TCO BTYPE=--) >> [ 1.091910] pc : add_interrupt_randomness+0x2e8/0x318 >> [ 1.092965] lr : add_interrupt_randomness+0x2e8/0x318 >> [ 1.094021] sp : ffff80001000be80 >> [ 1.094732] x29: ffff80001000be80 x28: ffff2d0c80209840 >> [ 1.095859] x27: 00000000137c3e3a x26: ffff8000100abdd0 >> [ 1.096978] x25: 0000000000000035 x24: ffff67918bda8000 >> [ 1.098100] x23: ffffc57c31923fe8 x22: 00000000fffedc14 >> [ 1.099224] x21: ffff2d0dbef796a0 x20: ffffc57c331d16a0 >> [ 1.100339] x19: ffffc57c33720a48 x18: 0000000000000010 >> [ 1.101459] x17: 0000000000000000 x16: 0000000000000002 >> [ 1.102578] x15: 00000000000000e7 x14: ffff80001000bb20 >> [ 1.103706] x13: 00000000ffffffea x12: ffffc57c337b56e8 >> [ 1.104821] x11: 0000000000000003 x10: ffffc57c3379d6a8 >> [ 1.105944] x9 : ffffc57c3379d700 x8 : 0000000000017fe8 >> [ 1.107073] x7 : c0000000ffffefff x6 : 0000000000000001 >> [ 1.108186] x5 : 0000000000057fa8 x4 : 0000000000000000 >> [ 1.109305] x3 : 00000000ffffffff x2 : ffffc57c337455d0 >> [ 1.110428] x1 : db8dc9c2a1e0f600 x0 : 0000000000000000 >> [ 1.111552] Call trace: >> [ 1.112083] add_interrupt_randomness+0x2e8/0x318 >> [ 1.113074] handle_irq_event_percpu+0x48/0x90 >> [ 1.114016] handle_irq_event+0x48/0xf8 >> [ 1.114826] handle_fasteoi_irq+0xa4/0x130 >> [ 1.115689] generic_handle_irq+0x30/0x48 >> [ 1.116528] __handle_domain_irq+0x64/0xc0 >> [ 1.117392] gic_handle_irq+0xc0/0x138 >> [ 1.118194] el1_irq+0xbc/0x180 >> [ 1.118870] arch_cpu_idle+0x20/0x30 >> [ 1.119630] default_idle_call+0x8c/0x350 >> [ 1.120479] do_idle+0x224/0x298 >> [ 1.121163] cpu_startup_entry+0x28/0x70 >> [ 1.121994] secondary_start_kernel+0x184/0x198 >> >> ... and I couldn't immediately spot why 32-bit arm would be >> different. >> > > Hmm, I actually meant both arm64 and ARM. > > Marc looked into this at my request a while ago, and I had a look > myself as well at the time, and IIRC, we both concluded that we don't > hit that code path. Darn. Yes, I remember checking this. Obviously, I need a new pair of glasses... M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel