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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2012-07-03 14:31:43 +0800
committerMarcelo Tosatti <mtosatti@redhat.com>2012-07-03 17:31:50 -0300
commit85b7059169e128c57a3a8a3e588fb89cb2031da1 (patch)
tree9934b741d6b66addd0b215e77ff60503e897cd02 /arch
parentf411930442e01f9cf1bf4df41ff7e89476575c4d (diff)
KVM: MMU: fix shrinking page from the empty mmu
Fix: [ 3190.059226] BUG: unable to handle kernel NULL pointer dereference at (null) [ 3190.062224] IP: [<ffffffffa02aac66>] mmu_page_zap_pte+0x10/0xa7 [kvm] [ 3190.063760] PGD 104f50067 PUD 112bea067 PMD 0 [ 3190.065309] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC [ 3190.066860] CPU 1 [ ...... ] [ 3190.109629] Call Trace: [ 3190.111342] [<ffffffffa02aada6>] kvm_mmu_prepare_zap_page+0xa9/0x1fc [kvm] [ 3190.113091] [<ffffffffa02ab2f5>] mmu_shrink+0x11f/0x1f3 [kvm] [ 3190.114844] [<ffffffffa02ab25d>] ? mmu_shrink+0x87/0x1f3 [kvm] [ 3190.116598] [<ffffffff81150c9d>] ? prune_super+0x142/0x154 [ 3190.118333] [<ffffffff8110a4f4>] ? shrink_slab+0x39/0x31e [ 3190.120043] [<ffffffff8110a687>] shrink_slab+0x1cc/0x31e [ 3190.121718] [<ffffffff8110ca1d>] do_try_to_free_pages This is caused by shrinking page from the empty mmu, although we have checked n_used_mmu_pages, it is useless since the check is out of mmu-lock Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/mmu.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index be3cea4407f..57e168e27b5 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3934,6 +3934,9 @@ static void kvm_mmu_remove_some_alloc_mmu_pages(struct kvm *kvm,
{
struct kvm_mmu_page *page;
+ if (list_empty(&kvm->arch.active_mmu_pages))
+ return;
+
page = container_of(kvm->arch.active_mmu_pages.prev,
struct kvm_mmu_page, link);
kvm_mmu_prepare_zap_page(kvm, page, invalid_list);