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Tue, 01 Dec 2020 06:43:50 -0800 (PST) Date: Tue, 1 Dec 2020 14:43:49 +0000 From: David Brazdil To: Mark Rutland Subject: Re: [PATCH v3 06/23] kvm: arm64: Add kvm-arm.protected early kernel parameter Message-ID: <20201201144349.bglz7yicc3peixe6@google.com> References: <20201126155421.14901-1-dbrazdil@google.com> <20201126155421.14901-7-dbrazdil@google.com> <20201127163254.zxdrszlveaxhluwn@bogus> <20201201131913.u7m2eifvtus74dra@google.com> <20201201140734.GA86881@C02TD0UTHF1T.local> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201201140734.GA86881@C02TD0UTHF1T.local> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201201_094353_094874_8D2F8755 X-CRM114-Status: GOOD ( 24.01 ) 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: Lorenzo Pieralisi , kernel-team@android.com, Jonathan Corbet , Catalin Marinas , Sudeep Holla , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Suzuki K Poulose , James Morse , linux-arm-kernel@lists.infradead.org, Marc Zyngier , Tejun Heo , Dennis Zhou , Christoph Lameter , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > > > be just me, but if you agree please update so that it doesn't give remote > > > idea that it is not valid on VHE enabled hardware. > > > > > > I was trying to run this on the hardware and was trying to understand the > > > details on how to do that. > > > > I see what you're saying, but !CONFIG_ARM64_VHE isn't accurate either. The > > option makes sense if: > > 1) all cores booted in EL2 > > == is_hyp_mode_available() > > 2) ID_AA64MMFR1_EL1.VH=0 or !CONFIG_ARM64_VHE > > == !is_kernel_in_hyp_mode() > > > > The former feels implied for KVM, the latter could be 'Valid if the kernel > > is running in EL1'? WDYT? > > I reckon we can avoid the restriction if we instead add an early stub > like with have for KASLR. That way we could parse the command line > early, and if necessary re-initialize EL2 and drop to EL1 before the > main kernel has to make any decisions about how to initialize things. > That would allow us to have a more general kvm-arm.mode option where a > single kernel Image could support: > > * "protected" mode on nVHE or VHE HW > * "nvhe" mode on nVHE or VHE HW > * "vhe" mode on VHE HW > > ... defaulting to VHE/nVHE modes depending on HW support. > > That would also be somewhat future-proof if we have to add other > variants of protected mode in future, as we could extend the mode option > with parameters for each mode. Agreed that 'mode' is a more future-proof flag and I would very much love to have an option to force nVHE on VHE HW. I however expect that the early stub would not be a trivial addition and would not want to get into that in this series. Could we agree on 'protected' as the only supported value for the time being? David _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel