KVM: x86/mmu: Allow yielding during MMU notifier unmap/zap, if possible

mainline inclusion
from mainline-v5.13-rc1
commit e1eed584
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=e1eed5847b09fe41d4db4b86f9d840aba869c905



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Let the TDP MMU yield when unmapping a range in response to a MMU
notification, if yielding is allowed by said notification.  There is no
reason to disallow yielding in this case, and in theory the range being
invalidated could be quite large.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210402005658.3024832-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>