On 08/11/2018 07:31, Yong Wu wrote:
Hi Robin,
After the commit ad67f5a6545f ("arm64: replace ZONE_DMA with
ZONE_DMA32"), we don't have ZONE_DMA in aarch64, but
__arm_v7s_alloc_table[1] use the GFP_DMA to expect the physical address
of pagetable should be 32bit.
Right now we meet a issue that the lvl1 pagetable PA is 0x1_3ab6_0000 in
the 4GB broad. then the IOMMU initialize failed.(This issue can be fixed
if we revert ad67f5a6545f.)
But that shouldn't actually be failing on MTK platforms anyway, right,
since your IOMMU is still capable of addressing that? Seems like we
overlooked that check in __arm_v7s_alloc_table(), where the conversion
by casting will want updating to something like
"iopte_to_paddr(paddr_to_iopte(...))" in patch #4 of your series.
I planed to add GFP_DMA32 for pagetable allocation. the level1 was
ok but level2 was failed. It looks that slab don't like GFP_DMA32[2].
this is the warning log:
=====
Unexpected gfp: 0x4 (GFP_DMA32). Fixing up to gfp: 0x488020 (GFP_ATOMIC|
__GFP_ZERO). Fix your code!
=====
I don't know why slab don't allow GFP_DMA32, the gfp flags seems only
be bypassed to alloc_page. Is it possible that let slab allow GFP_DMA32
for aarch64?
I had a bit of a look into it some time ago, and I don't recall seeing
any obvious reason that the kmem_cache API couldn't support ZONE_DMA32
in general (either via a separate SLAB_CACHE_DMA32, or just overloading
SLAB_CACHE_DMA depending on which of CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32
are enabled) - I guess that's just never been implemented since nobody
needed it before.
Robin.
We notice that this has been discussed[3]. but if we use alloc_page for
the level2 pagetable, It may waste lots of memory.
Any suggestion is appreciated.
Reported-by: Nicolas Boichat <drink...@chromium.org>
[1]
https://elixir.bootlin.com/linux/v4.20-rc1/source/drivers/iommu/io-pgtable-arm-v7s.c#L200
[2] https://elixir.bootlin.com/linux/v4.20-rc1/source/mm/internal.h#L37
[3] https://patchwork.kernel.org/patch/10474289/
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