Re: [PATCH v2 3/6] x86, mm, asm-gen: Add ioremap_wt() for WT

[Toshi Kani]

On Wed, 2014-09-10 at 11:29 -0700, Andy Lutomirski wrote:
> On Wed, Sep 10, 2014 at 9:51 AM, Toshi Kani <toshi.kani@xxxxxx> wrote:
 :
> > +#ifndef ARCH_HAS_IOREMAP_WT
> > +#define ioremap_wt ioremap_nocache
> > +#endif
> > +
> 
> This is a little bit sad.  I wouldn't be too surprised if there are
> eventually users who prefer WC or WB over UC if WT isn't available
> (and they'll want a corresponding way to figure out what kind of fence
> to use).

Right, this redirection is not ideal for the performance, but it is done
this way for the correctness.  WT & UC have strongly ordered writes, but
WB & WC do not.

Thanks,
-Toshi

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/