Re: [RFC PATCH crypto] AES: Add support to Intel AES-NI instructions

Herbert Xu
2008-12-16T23:31:54Z

On Mon, Dec 15, 2008 at 11:38:01PM +1100, Herbert Xu wrote:
> On Mon, Dec 15, 2008 at 04:21:06PM +1100, Herbert Xu wrote:
> >
> > > a. Do not touch SSE state in soft_irq
> > > b. Disable/restore soft_irq in kernel_fpu_begin/kernel_fpu_end
> > > c. Use a per-CPU data structure to save kernel FPU state during
> > > soft_irq.

> Here's another option
>
> d. When we're in interrupt context, schedule a task to perform
> the encryption asynchronously.

We can also hybridise b. and d.:

e. When we're in interrupt context, if TS is clear, then we defer
the operation to a thread. Otherwise if user-space has touched
the FPU we save the state, if not then we simply clear TS. In
either case we perform the operation immediately and then reset
TS if user-space didn't touch the FPU.

This is based on the fact that it should be fairly rare for us
to interrupt a kernel FPU/SSE operation. The common case would
be interrupting a user process or a kernel context which is not
engaging in any kernel FPU operations.

Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt