From: Sean Christopherson seanjc@google.com
commit b28cb0cd2c5e80a8c0feb408a0e4b0dbb6d132c5 upstream.
When zapping obsolete pages, update the running count of zapped pages regardless of whether or not the list has become unstable due to zapping a shadow page with its own child shadow pages. If the VM is backed by mostly 4kb pages, KVM can zap an absurd number of SPTEs without bumping the batch count and thus without yielding. In the worst case scenario, this can cause a soft lokcup.
watchdog: BUG: soft lockup - CPU#12 stuck for 22s! [dirty_log_perf_:13020] RIP: 0010:workingset_activation+0x19/0x130 mark_page_accessed+0x266/0x2e0 kvm_set_pfn_accessed+0x31/0x40 mmu_spte_clear_track_bits+0x136/0x1c0 drop_spte+0x1a/0xc0 mmu_page_zap_pte+0xef/0x120 __kvm_mmu_prepare_zap_page+0x205/0x5e0 kvm_mmu_zap_all_fast+0xd7/0x190 kvm_mmu_invalidate_zap_pages_in_memslot+0xe/0x10 kvm_page_track_flush_slot+0x5c/0x80 kvm_arch_flush_shadow_memslot+0xe/0x10 kvm_set_memslot+0x1a8/0x5d0 __kvm_set_memory_region+0x337/0x590 kvm_vm_ioctl+0xb08/0x1040
Fixes: fbb158cb88b6 ("KVM: x86/mmu: Revert "Revert "KVM: MMU: zap pages in batch""") Reported-by: David Matlack dmatlack@google.com Reviewed-by: Ben Gardon bgardon@google.com Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20220511145122.3133334-1-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/mmu.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -5821,6 +5821,7 @@ static void kvm_zap_obsolete_pages(struc { struct kvm_mmu_page *sp, *node; int nr_zapped, batch = 0; + bool unstable;
restart: list_for_each_entry_safe_reverse(sp, node, @@ -5853,11 +5854,12 @@ restart: goto restart; }
- if (__kvm_mmu_prepare_zap_page(kvm, sp, - &kvm->arch.zapped_obsolete_pages, &nr_zapped)) { - batch += nr_zapped; + unstable = __kvm_mmu_prepare_zap_page(kvm, sp, + &kvm->arch.zapped_obsolete_pages, &nr_zapped); + batch += nr_zapped; + + if (unstable) goto restart; - } }
/*