Re: [PATCH v8 01/14] riscv: prevent null-pointer dereference with sbi_remote_fence_i

From: Heiko Stübner
Date: Thu Apr 07 2022 - 14:51:03 EST

Am Donnerstag, 31. März 2022, 14:33:22 CEST schrieb Christoph Hellwig:
> On Thu, Mar 31, 2022 at 02:28:06PM +0200, Heiko Stübner wrote:
> > so essentially flushes the _local_ icache first and then tries to flush
> > caches on other cores, either via an ipi or via sbi.
> >
> > The remote-fence callback is set correctly during sbi_init().
> > The other cores are only brought up after sbi-init is done.
> >
> > So it's not really about error reporting but making sure that flush_icache_all()
> > does something sane even when still running on the first core.
> > As I assume the "all" means on all available cores (which would be the
> > core the system booted on).
> >
> > Does this make it clearer what this tries to solve?
> A little. Whatever code calls this early still seems broken to me
> and just just do a local flush, though.

Looking at this again made me realize that we don't need this patch
anymore at all.

In a previous revision the "main" alternatives apply-point was earlier,
triggering the issue when the generic patching-functions wanted to
flush the cache, but with the alternatives getting applied where they
are now, the issue is not triggered anymore.

And the "early" alternatives use a local flush anyway.