Re: [PATCH 1/3] arm64: spin-table: handle unmapped cpu-release-addrs

[Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>]

On Tuesday 29 July 2014 17:03:03 Mark Rutland wrote:
> On Tue, Jul 29, 2014 at 04:20:46PM +0100, Arnd Bergmann wrote:
> > On Tuesday 29 July 2014 11:15:45 Mark Salter wrote:
> > > > -
> > > > -     __flush_dcache_area(release_addr, sizeof(release_addr[0]));
> > > > +     writeq_relaxed(__pa(secondary_holding_pen), release_addr);
> > > > +     __flush_dcache_area(release_addr, sizeof(*release_addr));
> > > 
> > >        __flush_dcache_area((__force void *)release_addr, ... 
> > > 
> > > to avoid sparse warning.
> 
> Presumably we'd get this for the write_relaxed too?

writeq_relaxed() actually expects an __iomem  pointer

> > 
> > I think it would be cleaner to drop the __iomem annotation and use vmap()
> > rather than ioremap(). That requires having a 'struct page' though, which
> > I'm not sure you have.
> 
> As far as I am aware, we'd only have a struct page for memory falling in
> the linear map, so for the cases this patch is actually required we
> wouldn't have a struct page.
> 
> So it looks like I should just make release_addr a void __iomem *. Then
> this line can just be:

You mean make it a 'void *' instead of 'void __iomem *', right?

> __flush_dcache_area(release_addr, 8);
> 
> Where we could replace 8 with sizeof(u64), sizeof(__le64), etc if 8 is
> too magic.
> 
> How does that sound?

Not sure where you're getting at. Using a regular pointer sounds fine,
but then you have to cast the result of ioremap and do a manual
cpu_to_le64 conversion on the assignment.

Keeping the iomem annotation will also work,a nd then we only need
the cast in the __flush_dcache_area call.

	Arnd