x86/speculation/mmio: Reuse SRBDS mitigation for SBDS

stable inclusion
from stable-v5.10.123
commit 6df693dca31218f76c63b6fd4aa7b7db3bd6e049
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=6df693dca31218f76c63b6fd4aa7b7db3bd6e049



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commit a992b8a4 upstream

The Shared Buffers Data Sampling (SBDS) variant of Processor MMIO Stale
Data vulnerabilities may expose RDRAND, RDSEED and SGX EGETKEY data.
Mitigation for this is added by a microcode update.

As some of the implications of SBDS are similar to SRBDS, SRBDS mitigation
infrastructure can be leveraged by SBDS. Set X86_BUG_SRBDS and use SRBDS
mitigation.

Mitigation is enabled by default; use srbds=off to opt-out. Mitigation
status can be checked from below file:

  /sys/devices/system/cpu/vulnerabilities/srbds

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>