On Wed, Oct 06, 2021 at 03:15:51PM +0100, Andrew Cooper wrote:
> The case which goes wrong is this:
>
> 1. Zen1 (or earlier) and Zen2 (or later) in a migration pool
> 2. Linux boots on Zen2, probes and finds the absence of X86_BUG_NULL_SEL
> 3. Linux is then migrated to Zen1
>
> Linux is now running on a X86_BUG_NULL_SEL-impacted CPU while believing
> that the bug is fixed.
>
> The only way to address the problem is to fully trust the "no longer
> affected" CPUID bit when virtualised, because in the above case it would
> be clear deliberately to indicate the fact "you might migrate to
> somewhere which really is affected".
Yap, makes sense.
Thanks for taking the time - that's what I was looking for.
Please add to the commit message of the next version.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
