On Thu, Aug 11, 2011 at 11:08 AM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxxx> wrote: > On Thu, Aug 11, 2011 at 10:50:49AM -0400, Andy Lutomirski wrote: >> >>> This is pretty similar to the situation with the Intel AES code. >>> Over there they solved it by using the asynchronous interface and >>> deferring the processing to a work queue. >> >> I have vague plans to clean up extended state handling and make >> kernel_fpu_begin work efficiently from any context. (i.e. the first >> kernel_fpu_begin after a context switch could take up to ~60 ns on Sandy >> Bridge, but further calls to kernel_fpu_begin would be a single branch.) > > This is all well and good but you still need to deal with the > case of !irq_fpu_usable. I think I can even get rid of that. Of course, until that happens, code still needs to handle !irq_fpu_usable. (Also, calling these things kernel_fpu_begin() is dangerous. It's not actually safe to use floating-point instructions after calling kernel_fpu_begin. Integer SIMD instructions are okay, though. The issue is that kernel_fpu_begin doesn't initialize MXCSR, and there are MXCSR values that will cause any floating-point instruction to trap regardless of its arguments.) --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
