KVM: x86/mmu: Use an rwlock for the x86 MMU

mainline inclusion
from mainline-v5.12-rc1
commit 531810ca
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=531810caa9f4bc99ffbb90e09256792c56a6b07a



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Add a read / write lock to be used in place of the MMU spinlock on x86.
The rwlock will enable the TDP MMU to handle page faults, and other
operations in parallel in future commits.

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

Message-Id: <20210202185734.1680553-19-bgardon@google.com>
[Introduce virt/kvm/mmu_lock.h - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

conflict:
	arch/x86/kvm/mmu/mmu.c
	virt/kvm/dirty_ring.c
	virt/kvm/kvm_main.c
	fs/proc/etmem_scan.c

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