On 18 October 2016 at 15:16, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote:
> On Tue, 2016-10-18 at 15:08 +0100, Ard Biesheuvel wrote:
>>
>> + aead_req = *this_cpu_ptr(ccmp->reqs);
>> + if (!aead_req) {
>> + aead_req = kzalloc(reqsize + CCM_AAD_LEN, GFP_ATOMIC);
>> + if (!aead_req)
>> + return -ENOMEM;
>> + *this_cpu_ptr(ccmp->reqs) = aead_req;
>> + aead_request_set_tfm(aead_req, ccmp->tfm);
>> + }
>
> Hmm. Is it really worth having a per-CPU variable for each possible
> key? You could have a large number of those (typically three when
> you're a client on an AP, and 1 + 1 for each client when you're the
> AP).
>
> Would it be so bad to have to set the TFM every time (if that's even
> possible), and just have a single per-CPU cache?
>
That would be preferred, yes. The only snag here is that
crypto_alloc_aead() is not guaranteed to return the same algo every
time, which means the request size is not guaranteed to be the same
either. This is a rare corner case, of course, but it needs to be
dealt with regardless
