On Tue, Jun 1, 2010 at 6:07 AM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, May 31, 2010 at 09:04:00PM +0200, Andi Kleen wrote: >> > I mean how it is implemented now in crypto API, and I was almost >> > sure that aes-ni acceleration code uses cryptd (iow real asynchronous processing) >> > and also that not all CPU cores can run these instruction in parallel. >> >> I think you can configure it to use cryptd (or pcrypt), but it's not default >> and usually higher overhead. > > Right. The only reason aes-ni uses the async interface is to > work around the fact that you have to save FPU state when using > it. For dm-crypt you can consider it to be synchronous. The reason for aes-ni to use async interface is that the FPU/SSE instructions enclosed by kernel_fpu_begin and kernel_fpu_end is not reentranceable. That is, it is not safe to use FPU/SSE instructions in interrupt context, if the instructions are used in interrupted context. So irq_fpu_usable is used in the async interface of aes-ni, and go asynchronous implementation only if !irq_fpu_usable. In most instances, the async interface of aes-ni will run in synchronous mode. Best Regards, Huang Ying -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
