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Wed, 11 Nov 2020 13:29:29 +0000 MIME-Version: 1.0 Date: Wed, 11 Nov 2020 13:29:29 +0000 From: Marc Zyngier To: David Brazdil Subject: Re: [PATCH v1 07/24] kvm: arm64: Create nVHE copy of cpu_logical_map In-Reply-To: <20201111130321.qalrzfabdonrwvsz@google.com> References: <20201109113233.9012-1-dbrazdil@google.com> <20201109113233.9012-8-dbrazdil@google.com> <20201111130321.qalrzfabdonrwvsz@google.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <15a580e6ac06294ead8859fba8f51deb@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: dbrazdil@google.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, dennis@kernel.org, tj@kernel.org, cl@linux.com, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, qperret@google.com, ascull@google.com, qwandor@google.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kernel-team@android.com, Lorenzo Pieralisi , Andrew Walbran , Catalin Marinas , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Tejun Heo , Dennis Zhou , Christoph Lameter , Will Deacon , kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 2020-11-11 13:03, David Brazdil wrote: >> > +/* >> > + * nVHE copy of data structures tracking available CPU cores. >> > + * Only entries for CPUs that were online at KVM init are populated. >> > + * Other CPUs should not be allowed to boot because their features were >> > + * not checked against the finalized system capabilities. >> > + */ >> > +u64 __ro_after_init __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] >> > = INVALID_HWID }; >> >> I'm not sure what __ro_after_init means once we get S2 isolation. > > It is stretching the definition of 'init' a bit, I know, but I don't > see what > your worry is about S2? The intention is to mark this read-only for > .hyp.text > at runtime. With S2, the host won't be able to write to it after KVM > init. > Obviously that's currently not the case. More importantly, EL2 can write to it at any time, which is the bit I'm worried about, as it makes the annotation misleading. > One thing we might change in the future is marking it RW for some > initial > setup in a HVC handler, then marking it RO for the rest of uptime. That'd be a desirable outcome, and it would be consistent with the rest of the kernel. > >> >> > + >> > +u64 cpu_logical_map(int cpu) >> >> nit: is there any reason why "cpu" cannot be unsigned? The thought >> of a negative CPU number makes me shiver... > > Same here. That's how it's defined in kernel proper, so I went with > that. I'm happy to deviate from the kernel (give the function a different name if this clashes with existing include files). We can also fix the rest of the kernel (I've just written the trivial patch). >> >> > +{ >> > + if (cpu < 0 || cpu >= ARRAY_SIZE(__cpu_logical_map)) >> > + hyp_panic(); >> > + >> > + return __cpu_logical_map[cpu]; >> > +} >> > + >> > unsigned long __hyp_per_cpu_offset(unsigned int cpu) >> > { >> > unsigned long *cpu_base_array; >> >> Overall, this patch would make more sense closer it its use case >> (in patch 19). I also don't understand why this lives in percpu.c... > > I didn't think it called for adding another C file for this. How about > we > rename this file to smp.c? Would that make sense for both? Make that hyp-smp.c, please! M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm