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Commit 86fde74c authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Marcelo Tosatti
Browse files

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: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 9d3c92af

arch/x86/kvm/mmu.c

+8 −0
Original line number Diff line number Diff line
@@ -556,6 +556,14 @@ static int mmu_spte_clear_track_bits(u64 *sptep) 
		return 0;



	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)

		kvm_set_pfn_accessed(pfn);

	if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))