Since kvm_arch_prepare_memory_region() is called right after installing
the slot marked invalid, wraparound checking should be there to avoid
zapping mmio sptes when mmio generation is still MMIO_MAX_GEN - 1.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
---
This seems to be the simplest solution for fixing the off-by-one issue
we discussed before.
arch/x86/kvm/mmu.c | 5 +----
arch/x86/kvm/x86.c | 7 +++++++
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 0d094da..bf7af1e 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4383,11 +4383,8 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
/*
* The very rare case: if the generation-number is round,
* zap all shadow pages.
- *
- * The max value is MMIO_MAX_GEN - 1 since it is not called
- * when mark memslot invalid.
*/
- if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1))) {
+ if (unlikely(kvm_current_mmio_generation(kvm) >= MMIO_MAX_GEN)) {
printk_ratelimited(KERN_INFO "kvm: zapping shadow pages for mmio generation wraparound\n");
kvm_mmu_invalidate_zap_all_pages(kvm);
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7d71c0f..9ddd4ff 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7046,6 +7046,13 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
memslot->userspace_addr = userspace_addr;
}
+ /*
+ * In these cases, slots->generation has been increased for marking the
+ * slot invalid, so we need wraparound checking here.
+ */
+ if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE))
+ kvm_mmu_invalidate_mmio_sptes(kvm);
+
return 0;
}
--
1.7.9.5
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