[1/2] KVM: x86: Remove obsolete disabling of page faults in kvm_arch_vcpu_put()

Commit Message

Sean Christopherson Jan. 23, 2021, 12:03 a.m. UTC

Remove the disabling of page faults across kvm_steal_time_set_preempted()
as KVM now accesses the steal time struct (shared with the guest) via a
cached mapping (see commit b043138246a4, "x86/KVM: Make sure
KVM_VCPU_FLUSH_TLB flag is not missed".)  The cache lookup is flagged as
atomic, thus it would be a bug if KVM tried to resolve a new pfn, i.e.
we want the splat that would be reached via might_fault().

Signed-off-by: Sean Christopherson <[e-mail]>
---
 arch/x86/kvm/x86.c | 10 ----------
 1 file changed, 10 deletions(-)

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a8969a6dd06..3f4b09d9f25b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4031,15 +4031,6 @@  void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	if (vcpu->preempted && !vcpu->arch.guest_state_protected)
 		vcpu->arch.preempted_in_kernel = !kvm_x86_ops.get_cpl(vcpu);
 
-	/*
-	 * Disable page faults because we're in atomic context here.
-	 * kvm_write_guest_offset_cached() would call might_fault()
-	 * that relies on pagefault_disable() to tell if there's a
-	 * bug. NOTE: the write to guest memory may not go through if
-	 * during postcopy live migration or if there's heavy guest
-	 * paging.
-	 */
-	pagefault_disable();
 	/*
 	 * kvm_memslots() will be called by
 	 * kvm_write_guest_offset_cached() so take the srcu lock.
@@ -4047,7 +4038,6 @@  void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
 	kvm_steal_time_set_preempted(vcpu);
 	srcu_read_unlock(&vcpu->kvm->srcu, idx);
-	pagefault_enable();
 	kvm_x86_ops.vcpu_put(vcpu);
 	vcpu->arch.last_host_tsc = rdtsc();
 	/*