4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Suzuki K Poulose <suzuki.poul...@arm.com>

commit 7e5a672289c9754d07e1c3b33649786d3d70f5e4 upstream.

The mmu_notifier_release() callback of KVM triggers cleaning up
the stage2 page table on kvm-arm. However there could be other
notifier callbacks in parallel with the mmu_notifier_release(),
which could cause the call backs ending up in an empty stage2
page table. Make sure we check it for all the notifier callbacks.

Fixes: commit 293f29363 ("kvm-arm: Unmap shadow pagetables properly")
Reported-by: Alex Graf <ag...@suse.de>
Reviewed-by: Christoffer Dall <cd...@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>


---
 arch/arm/kvm/mmu.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1664,12 +1664,16 @@ static int kvm_test_age_hva_handler(stru
 
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
 {
+       if (!kvm->arch.pgd)
+               return 0;
        trace_kvm_age_hva(start, end);
        return handle_hva_to_gpa(kvm, start, end, kvm_age_hva_handler, NULL);
 }
 
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
 {
+       if (!kvm->arch.pgd)
+               return 0;
        trace_kvm_test_age_hva(hva);
        return handle_hva_to_gpa(kvm, hva, hva, kvm_test_age_hva_handler, NULL);
 }


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