On Mon, Nov 09, 2015 at 04:00:51PM +0800, Heyi Guo wrote:
> Hi All,
>
> In AARCH64 MMU configuration code, sharable attribute will be set to
> inner sharable when memory attribute is write back. However, I have
> 2 questions about this code:
> 1. Why is it set to inner sharable only when memory attribute is
> write back? Either write through or uncached will use non-shareable
> for TCR.
> 2. All memory regions will be set to none shareable in AARCH64 MMU
> configuration code, whatever cachable attribute they have (WB, WT or
> UC). In my opinion, TCR attribute should be kept consistent with the
> memory where translation tables are located, i.e.
> TCR_SH_NON_SHAREABLE will always be the proper attribute for TCR.
>
> So could you help to confirm whether there is anything wrong with the code?
I agree these need to be consistent.
However, looking at the AArch64 ArmConfigureMmu function, I'm also
confused as to why the code tries to deal with all possible memory
attributes. If the translation tables are not in write-back,
write-allocate memory, something is seriously wrong and we should
ASSERT and RETURN_UNSUPPORTED. I think I'll whip up a patch to do
that, on top of Ard's.
/
Leif
> Thanks.
>
> ArmPkg/Library/ArmLib/AArch64/AArch64Mmu.c
>
>
> if ((TranslationTableAttribute ==
> ARM_MEMORY_REGION_ATTRIBUTE_UNCACHED_UNBUFFERED) ||
> (TranslationTableAttribute ==
> ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_UNCACHED_UNBUFFERED)) {
> TCR |= TCR_SH_NON_SHAREABLE | TCR_RGN_OUTER_NON_CACHEABLE |
> TCR_RGN_INNER_NON_CACHEABLE;
> } else if ((TranslationTableAttribute ==
> ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK) ||
> (TranslationTableAttribute ==
> ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_BACK)) {
>
> ++ TCR |= **TCR_SH_INNER_SHAREABLE** |
> TCR_RGN_OUTER_WRITE_BACK_ALLOC | TCR_RGN_INNER_WRITE_BACK_ALLOC;
>
>
> } else if ((TranslationTableAttribute ==
> ARM_MEMORY_REGION_ATTRIBUTE_WRITE_THROUGH) ||
> (TranslationTableAttribute ==
> ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_THROUGH)) {
> TCR |= TCR_SH_NON_SHAREABLE | TCR_RGN_OUTER_WRITE_THROUGH |
> TCR_RGN_INNER_WRITE_THROUGH;
>
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