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KVM: MMU: track the refcount when unmap the page 

It will trigger a WARN_ON if the page has been freed but it is still
used in mmu, it can help us to detect mm bug early

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Xiao Guangrong 2012-07-17 21:52:52 +08:00 committed by Marcelo Tosatti
parent 9d3c92af47
commit 86fde74cf5
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kvm/mmu.c
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@ -556,6 +556,14 @@ static int mmu_spte_clear_track_bits(u64 *sptep)
return 0; return 0;
pfn = spte_to_pfn(old_spte); pfn = spte_to_pfn(old_spte);
/*
* KVM does not hold the refcount of the page used by
* kvm mmu, before reclaiming the page, we should
* unmap it from mmu first.
*/
WARN_ON(!kvm_is_mmio_pfn(pfn) && !page_count(pfn_to_page(pfn)));
if (!shadow_accessed_mask || old_spte & shadow_accessed_mask) if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn); kvm_set_pfn_accessed(pfn);
if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask)) if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))