Currently OVMF tries to rely on the base size advertised via the CPUID table entries corresponding to leaf 0xD, sub-leafs 0x0/0x1. This will generally work for KVM guests, but might not for other SEV-SNP hypervisor implementations. Make the handling more robust by simply using the base area size documented by the APM. Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> Acked-by: Jiewen Yao <jiewen.yao@intel.com> Acked-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Michael Roth <michael.roth@amd.com>