On June 15, 2018 2:14:50 PM UTC, Yu-cheng Yu yu-cheng.yu@intel.com wrote:

On Fri, 2018-06-15 at 14:11 +0200, Julian Stecklina wrote:

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Yu,

Regarding your patch to disable AVX with eager fpu disabled in the

4.4

...

stable queue:

https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree...

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Why would this be necessary? In the Intel SDM Vol 2, Chapter 2.4, FPU/SIMD instructions are grouped into different classes and for all

of

...

them CR0.TS triggers a #NM exception in all modes but real mode and virtual 8086 mode.

It seems to me lazy context switching of AVX is perfectly functional (disregarding the recently disclosed security issue). Am I missing something?

Julian

This is for MPX, not AVX.

Wrong link. There was another one for AVX, but I saw it got reverted. Nevermind then. ;)

Julian