KVM: arm64: Add templates for BHB mitigation sequences

stable inclusion
from stable-v4.19.236
commit a68912a3ae3413be5febcaa40e7e0ec1fd62adee
category: bugfix
bugzilla: 186460, https://gitee.com/src-openeuler/kernel/issues/I53MHA


CVE: CVE-2022-23960

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

KVM writes the Spectre-v2 mitigation template at the beginning of each
vector when a CPU requires a specific sequence to run.

Because the template is copied, it can not be modified by the alternatives
at runtime. As the KVM template code is intertwined with the bp-hardening
callbacks, all templates must have a bp-hardening callback.

Add templates for calling ARCH_WORKAROUND_3 and one for each value of K
in the brancy-loop. Identify these sequences by a new parameter
template_start, and add a copy of install_bp_hardening_cb() that is able to
install them.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Conflicts:
    arch/arm64/include/asm/cpucaps.h

Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Liao Chang <liaochang1@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>