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KVM: x86: Remove obsolete disabling of page faults in kvm_arch_vcpu_put() 

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 b043138246, "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 <seanjc@google.com>
Message-Id: <20210123000334.3123628-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-01-22 16:03:33 -08:00 committed by Paolo Bonzini
parent bd2fae8da7
commit 19979fba9b
1 changed files with 0 additions and 10 deletions
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10
arch/x86/kvm/x86.c
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@ -4040,15 +4040,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
if (vcpu->preempted && !vcpu->arch.guest_state_protected) if (vcpu->preempted && !vcpu->arch.guest_state_protected)
vcpu->arch.preempted_in_kernel = !kvm_x86_ops.get_cpl(vcpu); 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_memslots() will be called by
* kvm_write_guest_offset_cached() so take the srcu lock. * kvm_write_guest_offset_cached() so take the srcu lock.
@ -4056,7 +4047,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
idx = srcu_read_lock(&vcpu->kvm->srcu); idx = srcu_read_lock(&vcpu->kvm->srcu);
kvm_steal_time_set_preempted(vcpu); kvm_steal_time_set_preempted(vcpu);
srcu_read_unlock(&vcpu->kvm->srcu, idx); srcu_read_unlock(&vcpu->kvm->srcu, idx);
pagefault_enable();
kvm_x86_ops.vcpu_put(vcpu); kvm_x86_ops.vcpu_put(vcpu);
vcpu->arch.last_host_tsc = rdtsc(); vcpu->arch.last_host_tsc = rdtsc();
/* /*