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KVM: x86/mmu: Voluntarily reschedule as needed when zapping MMIO sptes

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Call cond_resched_lock() when zapping MMIO to reschedule if needed or to
release and reacquire mmu_lock in case of contention.  There is no need
to flush or zap when temporarily dropping mmu_lock as zapping MMIO sptes
is done when holding the memslots lock and with the "update in-progress"
bit set in the memslots generation, which disables MMIO spte caching.
The walk does need to be restarted if mmu_lock is dropped as the active
pages list may be modified.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-02-05 13:01:24 -08:00 committed by Paolo Bonzini
parent 4771450c34
commit 571c5af06e
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kvm/mmu.c
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@ -5954,7 +5954,8 @@ restart:
list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
if (!sp->mmio_cached)
continue;
if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list) ||
cond_resched_lock(&kvm->mmu_lock))
goto restart;
}