Messages in this thread | | | From | Anup Patel <> | Date | Wed, 22 Aug 2018 20:54:51 +0530 | Subject | Re: [RFC PATCH 3/5] RISC-V: Add cpu_operatios structure |
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On Wed, Aug 22, 2018 at 11:33 AM, Christoph Hellwig <hch@infradead.org> wrote: > On Tue, Aug 21, 2018 at 10:34:38PM +0530, Anup Patel wrote: >> The cpu_operations is certainly required because SOC vendors will add >> vendor-specific mechanism to selectively bringing-up CPUs/HARTs instead >> of all CPUs entering Linux kernel simultaneously. In fact, we might also end-up >> having CPU ON/OFF operations in SBI. > > Your forgot an essential part in your analysis: Right now we only have > one single way to deal with cpu on/offlining, and that is the dummy WFI > kind. Once other ways show up we can build proper infrastructure, but > until then this is just a white elephant as we have no idea how these > abstractions will look like. > > And my hope is that we'll just see new SBI calls, in which case we'll > just need SBI and dummy version and can avoid all the indirect calls.
IMHO, rather than waiting for new CPU ON/OFF methods to come-up we can keep the cpu_operations ready. Also, we are not re-inventing anything here which we might have to discard later because cpu_operations are already tried and hardened for Linux ARM64.
I agree with you that in long-term SBI-based CPU ON/OFF will be widely used. Most likely we will have at-least two CPU ON/OFF methods: 1. Existing lottery based spinning 2. New SBI calls
Regards, Anup
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