On 28.08.2025 17:03, Andrew Cooper wrote: > ... disabled by default. There is a lot of work before FRED can be enabled by > default. > > One part of FRED, the LKGS (Load Kernel GS) instruction, is enumerated > separately but is mandatory as FRED disallows the SWAPGS instruction. > Normally, we'd have to check both CPUID bits, but Xen does not use GS like > most other software, and can manage without the LKGS instruction. > > FRED formally removes the use of Ring1 and Ring2, meaning we cannot run 32bit > PV guests. Therefore, don't enable FRED by default in shim mode. OTOH, if > FRED is active, then PV32 needs disabling like with CET. > > No functional change. > > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
Reviewed-by: Jan Beulich <jbeul...@suse.com>
