Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map when adding them to the RMP table

Borislav Petkov
2024-01-12T20:08:36Z

On Fri, Jan 12, 2024 at 12:00:01PM -0800, Dave Hansen wrote:
> On 12/30/23 08:19, Michael Roth wrote:
> > If the kernel uses a 2MB directmap mapping to write to an address, and
> > that 2MB range happens to contain a 4KB page that set to private in the
> > RMP table, that will also lead to a page-fault exception.
>
> I thought we agreed long ago to just demote the whole direct map to 4k
> on kernels that might need to act as SEV-SNP hosts. That should be step
> one and this can be discussed as an optimization later.

What would be the disadvantage here? Higher TLB pressure when running
kernel code I guess...

--
Regards/Gruss,
Boris.