x86/speculation/srbds: Update SRBDS mitigation selection

stable inclusion
from stable-v5.10.123
commit cf1c01a5e4c3e269b9211ae2ef0a57f8c9474bfc
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5D5RS
CVE: CVE-2022-21123,CVE-2022-21125,CVE-2022-21166

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.10.y&id=cf1c01a5e4c3e269b9211ae2ef0a57f8c9474bfc



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

commit 22cac9c6 upstream

Currently, Linux disables SRBDS mitigation on CPUs not affected by
MDS and have the TSX feature disabled. On such CPUs, secrets cannot
be extracted from CPU fill buffers using MDS or TAA. Without SRBDS
mitigation, Processor MMIO Stale Data vulnerabilities can be used to
extract RDRAND, RDSEED, and EGETKEY data.

Do not disable SRBDS mitigation by default when CPU is also affected by
Processor MMIO Stale Data vulnerabilities.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>
Reviewed-by: Zhang Jianhua <chris.zjh@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Liao Chang <liaochang1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>