KVM: x86/mmu: Use atomic ops to set SPTEs in TDP MMU map

mainline inclusion
from mainline-v5.12-rc1
commit 9a77daac
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I7S3VQ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9a77daacc87dee9fd63e31243f21894132ed8407



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

To prepare for handling page faults in parallel, change the TDP MMU
page fault handler to use atomic operations to set SPTEs so that changes
are not lost if multiple threads attempt to modify the same SPTE.

Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>

Message-Id: <20210202185734.1680553-21-bgardon@google.com>
[Document new locking rules. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

conflict:
	arch/x86/include/asm/kvm_host.h

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>