On Mon, Oct 16, 2023 at 08:27:34AM -0500, Michael Roth wrote:
> From: Kim Phillips <kim.phillips@xxxxxxx>
>
> Without SEV-SNP, Automatic IBRS protects only the kernel. But when
> SEV-SNP is enabled, the Automatic IBRS protection umbrella widens to all
> host-side code, including userspace. This protection comes at a cost:
> reduced userspace indirect branch performance.
>
> To avoid this performance loss, don't use Automatic IBRS on SEV-SNP
> hosts. Fall back to retpolines instead.
>
> Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
> [mdr: squash in changes from review discussion]
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> ---
> arch/x86/kernel/cpu/common.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
