KVM: x86/mmu: Use fast invalidate mechanism to zap MMIO sptes

KVM: x86/mmu: Use fast invalidate mechanism to zap MMIO sptes

Use the fast invalidate mechasim to zap MMIO sptes on a MMIO generation
wrap.  The fast invalidate flow was reintroduced to fix a livelock bug
in kvm_mmu_zap_all() that can occur if kvm_mmu_zap_all() is invoked when
the guest has live vCPUs.  I.e. using kvm_mmu_zap_all() to handle the
MMIO generation wrap is theoretically susceptible to the livelock bug.

This effectively reverts commit a044326c88bb9 ("Revert "KVM: MMU: drop
kvm_mmu_zap_mmio_sptes""), i.e. restores the behavior of commit
da48d1aefa4d4 ("KVM: MMU: drop kvm_mmu_zap_mmio_sptes").

Note, this actually fixes commit b9000e9a9fc83 ("KVM: x86/mmu:
Voluntarily reschedule as needed when zapping MMIO sptes"), but there
is no need to incrementally revert back to using fast invalidate, e.g.
doing so doesn't provide any bisection or stability benefits.

Fixes: b9000e9a9fc83 ("KVM: x86/mmu: Voluntarily reschedule as needed when zapping MMIO sptes")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>