On Thu, Apr 07, 2022 at 07:40:59PM +0800, Herbert Xu wrote: > On Thu, Apr 07, 2022 at 12:01:02PM +0100, Catalin Marinas wrote: > > The only issue is whether the compiler gets confused by a pointer to a > > structure with a smaller alignment than alignof(struct ...). I don't see > > a performance or correctness issue on arm64 here. It would be a problem > > if instead of 16 we went down to 8 or 4 due to unaligned accesses but > > from 128 to 64 (or even 16), I don't think it matters. > > The issue is that there's code in the Crypto API which assumes > that all pointers returned by kmalloc are aligned to CRYPTO_MINALIGN, > if you break that then all that code would need to be modified. I'm not familiar with the crypto API, trying to make sense of it now ;). I can see in many cases that the kmalloc() caller aligns the requested size to something like crypto_tfm_ctx_alignment(). So this would guarantee a kmalloc() object aligned to CRYPTO_MINALIGN. > However, I think it's better to change the code that assumes > CRYPTO_MINALIGN guarantees DMA alignment. I saw Ard already started to refactor some of these. But in the meantime are there cases where the crypto code does a kmalloc() of less than CRYPTO_MINALIGN and expects it to be CRYPTO_MINALIGN aligned? -- Catalin
