Re: [PATCH 0/5] i387: stable kernel backport

[Willy Tarreau]

On Thu, Feb 23, 2012 at 02:38:42PM -0800, Linus Torvalds wrote:
> On Thu, Feb 23, 2012 at 2:27 PM, Willy Tarreau <w@xxxxxx> wrote:
> >
> > OK so indeed I will only be able to check that it boots :-/
> 
> Well, we could do some trivial test-harness that just forces the issue
> with regular timer interrupts (and even without AES-NI). I think Peter
> talked about that when we were trying to hunt it down - but I think he
> was then able to reproduce the problem without anything special and we
> dropped it.
> 
> Essentially, just doing something like
> 
>     if (irq_fpu_usable()) {
>         kernel_fpu_begin();
>         kernel_fpu_end();
>     }
> 
> in do_irq() and do_softirq() would stress-test things even without
> wireless, and even without AES-NI.

Interesting...

> You'd still need an x86-32 machine to test on, because x86-64 was
> immune to this issue.
> 
> But yeah, the impact of this seems to be small enough that for older
> kernels (which are likely used on older systems for maintenance
> anyway) disabling AES-NI on x86-32 really might be the way to go.

I agree. I don't know anybody using AES-NI on purpose on older x86-32
systems!

Willy

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/