Re: [PATCH v2 1/2] x86/cpu: Disable CR pinning during CPU bringup

[Chang S. Bae]

On 3/12/2026 7:20 AM, Dave Hansen wrote:
> On 3/12/26 07:08, Nikunj A. Dadhania wrote:
> > 1) Back-porting complexity: The current issue affects kernels (6.9+)
> >     where SEV-SNP guests fail to boot with FRED enabled. A simpler fix would
> >     be easier to backport and verify across stable branches.
>
> The simplest fix is to disable FRED on those kernels, fwiw.

In addition to this,

On SEV systems, early exceptions appear to be expected in practice while 
CR4.FSGSBASE=0. So, at the moment, it also looks safe and simple to 
disable the feature until when those entry paths are adjusted to 
tolerate that case.

Currently, those entry paths are patched to use FSGSBASE instructions 
regardless of the CR4 setting. That inflexibility appears to make it 
broken in the first place. I’d take a look and come back with something 
reviewable.