x86/boot/compressed/64: Check SEV encryption in the 32-bit boot-path

stable inclusion
from stable-5.10.40
commit d28aa3c157363f23a476d3bea87335f1ac016a67
bugzilla: 51882
CVE: NA

--------------------------------

commit fef81c86 upstream.

Check whether the hypervisor reported the correct C-bit when running
as an SEV guest. Using a wrong C-bit position could be used to leak
sensitive data from the guest to the hypervisor.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210312123824.306-8-joro@8bytes.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>