On 02/01/2014 11:27 AM, Linus Torvalds wrote:
(a) "we don't want to restore at all, because once the kernel starts
using math, it might do so a lot, and saving/restoring is a bad idea":
void __kernel_fpu_end(void)
{
stts();
}
*or*
Quite frankly, I'd almost lean towards (a). Comments? Does anybody
have any loads where the kernel does a lot of fpu stuff (ie network
encryption using the hw engines or something)? I'd really like to hear
if it makes a difference..
This will obviously not protect eageronly features (MPX, LWP, ...) so
this means those features are permanently unavailable to the kernel,
even inside kernel_fpu_begin/end. Now, currently I don't think we have
any plans to use those in the kernel (at least not in a way where
kernel_fpu_begin/end makes sense as bracketing), but it is something
worth keeping in mind.
-hpa
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