RE: Bogus struct page layout on 32-bit

From: David Laight
Date: Sat Apr 17 2021 - 09:09:01 EST

From: Grygorii Strashko
> Sent: 16 April 2021 10:27
> Sry, for delayed reply.
> The TI platforms am3/4/5 (cpsw) and Keystone 2 (netcp) can do only 32bit DMA even in case of LPAE
> (dma-ranges are used).
> Originally, as I remember, CONFIG_ARCH_DMA_ADDR_T_64BIT has not been selected for the LPAE case
> on TI platforms and the fact that it became set is the result of multi-paltform/allXXXconfig/DMA
> optimizations and unification.
> (just checked - not set in 4.14)
> Probable commit 4965a68780c5 ("arch: define the ARCH_DMA_ADDR_T_64BIT config symbol in lib/Kconfig").
> The TI drivers have been updated, finally to accept ARCH_DMA_ADDR_T_64BIT=y by using things like
> (__force u32)
> for example.

Hmmm using (__force u32) is probably wrong.
If an address +length >= 2**32 can get passed then the IO request
needs to be errored (or a bounce buffer used).

Otherwise you can get particularly horrid corruptions.


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