Re: [PATCH] KVM: arm/arm64: Fix young bit from mmu notifier

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On 2020-01-21 05:56, Gavin Shan wrote:
kvm_test_age_hva() is called upon mmu_notifier_test_young(), but wrong
address range has been passed to handle_hva_to_gpa(). With the wrong
address range, no young bits will be checked in handle_hva_to_gpa().
It means zero is always returned from mmu_notifier_test_young().

This fixes the issue by passing correct address range to the underly
function handle_hva_to_gpa(), so that the hardware young (access) bit
will be visited.

Cc: stable@xxxxxxxxxxxxxxx # v4.1+
Fixes: 35307b9a5f7e ("arm/arm64: KVM: Implement Stage-2 page aging")
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
 virt/kvm/arm/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 0b32a904a1bb..a2777efb558e 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -2147,7 +2147,8 @@ 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);
+	return handle_hva_to_gpa(kvm, hva, hva + PAGE_SIZE,
+				 kvm_test_age_hva_handler, NULL);
 }

 void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)

I knew this start/end thing (instead of start/size) would bite us
one of these days. Terribly embarrassing. On the other hand, who
really wants to swap things out? ;-)

Out of curiosity, how did you find this one?

Thanks,

        M.
--
Jazz is not dead. It just smells funny...
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