Hi Andy,

On Fri, Sep 21, 2018 at 5:23 AM Andy Lutomirski [off-list ref] wrote:

At the risk on suggesting something awful: on x86_64, since we turn preemption off for simd, it wouldn’t be *completely* insane to do the crypto on the irq stack. It would look like:

kernel_fpu_call(func, arg);

And this helper would disable preemption, enable FPU, switch to the irq stack, call func(arg), disable FPU, enable preemption, and return. And we can have large IRQ stacks.

I refuse to touch this with a ten-foot pole until the lazy FPU restore patches land.

Haha. That's fun, and maybe we'll do that at some point, but I have
some other reasons too for being on a workqueue now.

All that being said, why are these frames so large?  It sounds like something may be spilling that ought not to.

They're not. Well, they're not anymore. I had a silly thing before
like "u8 buffer[1 << 12]" in some debugging code, which is what
prompted the ccflag-y addition. I cleaned up the mistakes like that
and frames are now reasonable everywhere. Non-issue.

Jason