On Mon, Jun 10, 2024 at 09:42:58AM -0700, Eric Biggers wrote: > > I understand that you think the ahash based API would make it easier to add > multibuffer support to "authenc(hmac(sha256),cbc(aes))" for IPsec, which seems > to be a very important use case for you (though it isn't relevant to nearly as > many systems as dm-verity and fsverity are). Regardless, the reality is that it > would be much more difficult to take advantage of multibuffer crypto in the > IPsec authenc use case than in dm-verity and fsverity. authenc uses multiple > underlying algorithms, AES-CBC and HMAC-SHA256, that would both have to use > multibuffer crypto in order to see a significant benefit, seeing as even if the > SHA-256 support could be wired up through HMAC-SHA256, encryption would be > bottlenecked on AES-CBC, especially on Intel CPUs. It also looks like the IPsec > code would need a lot of updates to support multibuffer crypto. The linked-request thing feeds nicely into networking. In fact that's where I got the idea of linking them from. In networking a large GSO (currently limited to 64K but theoretically we could make it unlimited) packet is automatically split up into a linked list of MTU-sized skb's. Therefore if we switched to a linked-list API networking could give us the buffers with minimal changes. BTW, I found an old Intel paper that claims through their multi- buffer strategy they were able to make AES-CBC-XCBC beat AES-GCM. I wonder if we could still replicate this today: https://github.com/intel/intel-ipsec-mb/wiki/doc/fast-multi-buffer-ipsec-implementations-ia-processors-paper.pdf > Ultimately, I need to have dm-verity and fsverity be properly optimized in the > downstreams that are most relevant to me. If you're not going to allow the > upstream crypto API to provide the needed functionality in a reasonable way, > then I'll need to shift my focus to getting this patchset into downstream > kernels such as Android and Chrome OS instead. I totally understand that this is your priority. But please give me some time to see if we can devise something that works for both scenarios. Thanks, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
