Re: [RFC PATCH 3/5] RISC-V: Add cpu_operatios structure
From: Palmer Dabbelt
Date: Wed Aug 22 2018 - 13:16:50 EST
On Tue, 21 Aug 2018 23:03:53 PDT (-0700), Christoph Hellwig 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.
Yes, the goal here is to define one good interface via the SBI. We've got a
session at Plumbers this year and one of the blocks is to sit down and talk
about this API, hopefully we can make some headway while there.