Re: Rewording of Setting IA32_XFD[18] (Re: Thoughts of AMX KVM support based on latest kernel)

[Thomas Gleixner]

Jun,

On Wed, Dec 08 2021 at 00:50, Jun Nakajima wrote:
>> On Nov 19, 2021, at 7:41 AM, Nakajima, Jun <jun.nakajima@xxxxxxxxx> wrote:
>> I’ll work with the H/W team on those (i.e. rewording and the component 17 issue).
>> 
>
> The following is a possible documentation update that may convey the
> rewording you requested.  Does this (the last sentence, “In addition,
> “) work for you?
>
> 3.3 RECOMMENDATIONS FOR SYSTEM SOFTWARE
>
> System software may disable use of Intel AMX by clearing XCR0[18:17],
> by clearing CR4.OSXSAVE, or by setting IA32_XFD[18]. System software
> should initialize AMX state (e.g., by executing TILERELEASE) when
> doing so because maintaining AMX state in a non-initialized state may
> have negative power and performance implications. In addition,
> software should not rely on the state of the tile data after setting
> IA32_XFD[18]; software should always reload or reinitialize the tile
> data after clearing IA32_XFD[18].

looks good to me.

Thanks,

        tglx