On Fri, 15 Apr 2022 at 08:51, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Apr 13, 2022 at 09:47:29AM +0100, Catalin Marinas wrote: > > > > With my series, there is no change to the value of CRYPTO_MINALIGN for > > arm64 or any other architecture, so point 3 is unaffected. The series > > does change the kmalloc() alignment and that may be smaller than > > CRYPTO_MINALIGN but neither of points 1 or 2 above are affected since > > (a) we still have a sufficiently large ARCH_KMALLOC_MINALIGN of 64 and > > (b) the kmalloc'ed buffers are safe for non-coherent DMA. > > > > Herbert, Ard, if I missed anything please let me know but based on my > > understanding, this series is safe for the crypto code. > > Sorry, but you can't change CRYPTO_MINALIGN to a value greater > than the minimum alignment returned by kmalloc. That simply > doesn't work. There is no magic in the Crypto API that makes > this work. > I'm not sure I understand what would go wrong if that assumption no longer holds, but if CRYPTO_MINALIGN needs to remain equal to ARCH_KMALLOC_MINALIGN, let's at least decouple it from ARCH_DMA_MINALIGN, as I do in my series. As I pointed out before, ARCH_DMA_MINALIGN has nothing to do with DMA addressing capabilities of individual masters, it is simply a worst case cacheline size that needs to be taken into account to avoid corruption when doing cache invalidation for non-cache coherent inbound DMA. I'll rename the flag I proposed from CRYPTO_ALG_NEED_DMA_ALIGNMENT to CRYPTO_ALG_NEED_DMA_PADDING to make this clearer, and given that only a few drivers should be relying on DMA to write into request/TFM context structures, hopefully we can fix those to stop doing that, and get rid of this flag again entirely.
