x86/kvm: Teardown PV features on boot CPU as well

mainline inclusion
from mainline-v5.13-rc2
commit 8b79feff
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I990AA
CVE: CVE-2021-47112

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8b79feffeca28c5459458fe78676b081e87c93a4



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

Various PV features (Async PF, PV EOI, steal time) work through memory
shared with hypervisor and when we restore from hibernation we must
properly teardown all these features to make sure hypervisor doesn't
write to stale locations after we jump to the previously hibernated kernel
(which can try to place anything there). For secondary CPUs the job is
already done by kvm_cpu_down_prepare(), register syscore ops to do
the same for boot CPU.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>