Re: [PATCH 6/6] alpha: invalidate the local context in flush_icache_user_page()

[Magnus Lindholm]

On Mon, Aug 10, 2026 at 5:03 AM Matt Turner <mattst88@xxxxxxxxx> wrote:

>
> ipi_flush_icache_page() also doesn't issue an imb() here, so I'm
> guessing it's not actually needed... but I could see why it might be.
> Any theories?

Yes, ipi_flush_icache_page() intentionally doesn't execute imb().
Alpha's userspace I-cache flush relies on changing/invalidation of
the ASN rather than physically invalidating the I-cache. The old
entries can stay because they're tagged with the old ASN. An imb()
is only required when ASNs wrap and can be reused, and
__get_new_mm_context() already does one in that case.
The problem patch 6 fixes is that the caller was omitted from this
ASN-invalidating protocol when the target mm wasn't active locally.

Magnus