On Sat, Nov 14, 2015 at 08:04:19PM +0100, Ard Biesheuvel wrote:
> On 14 November 2015 at 15:23, Ard Biesheuvel <[email protected]>
> wrote:
> >> I have an issue with this commit too on my ARMv7 device.
> >> It causes the whole system to get extremely slow.
> >
> > OK, thanks for the report.
> >
> > This means I will have to update the v7 code to use 'inner shareable'
> > explicitly, rather than the unqualified 'shareable' which most likely
> > implies outer shareable.
>
> Turns out it doesn't. According to the v7 ARM ARM:
>
> """
> In a VMSA implementation, Normal memory that has the Shareable
> attribute but not the Outer Shareable
> attribute assigned is described as having the Inner Shareable attribute.
> """
>
> and in addition, TEX remap is explicitly disallowed by the UEFI
> bindings for ARM
>
> Perhaps Leif or Mark have any insights to share on this topic?
Well, reality is that the binary Shareable attribute on the short
descriptor format is the hallmark of a non-coherent interconnect
(outside of the potentially multi-core processor which will be
coherent internally).
So yes, you need the long descriptor format in order to define
inner-shareable or outer-shareable attributes separately, and that is
currently only implemented for AArch64.
Apologies for not spotting that on review.
/
Leif
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