Re: [PATCH v12 19/37] x86/fred: Update MSR_IA32_FRED_RSP0 during task switch

Borislav Petkov
2023-11-13T18:30:26Z

On Mon, Nov 13, 2023 at 12:36:04PM -0500, H. Peter Anvin wrote:
> A resource cannot be consumed after the value has been written; this
> is the only necessary level of serialization, equivalent to, say, RAX.

Lemme see if I understand this correctly using this context as an
example: after this MSR_IA32_FRED_RSP0 write, any FRED events determined
to be delivered to level 0 will use this new task stack ptr?

And since the new task is not running yet and the old one isn't running
either, we're fine here. So the "serialization point" I was talking
about above is bollocks.

Close? :)

> A serializing instruction stops the entire pipeline until everything
> has retired and any stores have become globally visible.

Right, we don't need that here.

Thx.

--
Regards/Gruss,
Boris.