When poweroff L1 Guest with L2 guset on L1, it exists a path to trigger a bad_page bug_on. !page_count(pfn_to_page(pfn)) Warning in mmu_spte_clear_track_bits will appear before,then it may set A/D bit for the freed page and trigger a bad_page bug_on. Signed-off-by: Peng Hao <peng.hao2@xxxxxxxxxx> --- arch/x86/kvm/mmu.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index eca30c1..398de96 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -711,12 +711,8 @@ static int mmu_spte_clear_track_bits(u64 *sptep) 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_reserved_pfn(pfn) && !page_count(pfn_to_page(pfn))); + if (!page_count(pfn_to_page(pfn))) + return 1; if (is_accessed_spte(old_spte)) kvm_set_pfn_accessed(pfn); -- 1.8.3.1
