Re: [PATCH] arm64: mm: Fix memmap to be initialized for the entire section

Robert Richter
2016-11-24T14:11:49Z

On 24.11.16 13:58:30, Ard Biesheuvel wrote:
> On 24 November 2016 at 13:51, Robert Richter <robert.richter@cavium.com> wrote:
> > On 24.11.16 13:44:31, Ard Biesheuvel wrote:
> >> On 24 November 2016 at 13:42, Robert Richter <robert.richter@cavium.com> wrote:
> >> > On 23.11.16 21:25:06, Ard Biesheuvel wrote:
> >> >> Why? MEMREMAP_WB is used often, among other things for mapping
> >> >> firmware tables, which are marked as NOMAP, so in these cases, the
> >> >> linear address is not mapped.
> >> >
> >> > If fw tables are mapped wb, that is wrong and needs a separate fix.
> >> >
> >>
> >> Why is that wrong?
> >
> > The whole issue with mapping acpi tables is not marking them cachable,
> > what wb does.
>
> What 'issue'?
>
> > Otherwise we could just use linear mapping for those mem
> > ranges.
> >
>
> Regions containing firmware tables are owned by the firmware, and it
> is the firmware that tells us which memory attributes we are allowed
> to use. If those attributes include WB, it is perfectly legal to use a
> cacheable mapping. That does *not* mean they should be covered by the
> linear mapping. The linear mapping is read-write-non-exec, for
> instance, and we may prefer to use a read-only mapping and/or
> executable mapping.

Ok, I am going to fix try_ram_remap().

Are there other concerns with this patch?

Thanks,

-Robert