Date: Thu, 24 Nov 2016 15:11:49 +0100
From: Robert Richter <robert.richter@cavium.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
CC: Will Deacon <will.deacon@arm.com>, Robert Richter <rric@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        David Daney <david.daney@cavium.com>,
        Hanjun Guo <hanjun.guo@linaro.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: mm: Fix memmap to be initialized for the entire
 section
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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