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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2013-05-30 20:36:28 -0400
committerGleb Natapov <gleb@redhat.com>2013-06-05 05:33:18 -0400
commitf34d251d66ba263c077ed9d2bbd1874339a4c887 (patch)
tree369daaa407c8fa60f836a25fe64568b860a0316b /arch/x86/kvm/mmu.c
parente7d11c7a894986a13817c1c001e1e7668c5c4eb4 (diff)
KVM: MMU: collapse TLB flushes when zap all pages
kvm_zap_obsolete_pages uses lock-break technique to zap pages, it will flush tlb every time when it does lock-break We can reload mmu on all vcpus after updating the generation number so that the obsolete pages are not used on any vcpus, after that we do not need to flush tlb when obsolete pages are zapped It will do kvm_mmu_prepare_zap_page many times and use one kvm_mmu_commit_zap_page to collapse tlb flush, the side-effects is that causes obsolete pages unlinked from active_list but leave on hash-list, so we add the comment around the hash list walker Note: kvm_mmu_commit_zap_page is still needed before free the pages since other vcpus may be doing locklessly shadow page walking Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'arch/x86/kvm/mmu.c')
-rw-r--r--arch/x86/kvm/mmu.c33
1 files changed, 30 insertions, 3 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fe9d6f10e7a9..674c0442ac89 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1654,6 +1654,16 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
1654static void kvm_mmu_commit_zap_page(struct kvm *kvm, 1654static void kvm_mmu_commit_zap_page(struct kvm *kvm,
1655 struct list_head *invalid_list); 1655 struct list_head *invalid_list);
1656 1656
1657/*
1658 * NOTE: we should pay more attention on the zapped-obsolete page
1659 * (is_obsolete_sp(sp) && sp->role.invalid) when you do hash list walk
1660 * since it has been deleted from active_mmu_pages but still can be found
1661 * at hast list.
1662 *
1663 * for_each_gfn_indirect_valid_sp has skipped that kind of page and
1664 * kvm_mmu_get_page(), the only user of for_each_gfn_sp(), has skipped
1665 * all the obsolete pages.
1666 */
1657#define for_each_gfn_sp(_kvm, _sp, _gfn) \ 1667#define for_each_gfn_sp(_kvm, _sp, _gfn) \
1658 hlist_for_each_entry(_sp, \ 1668 hlist_for_each_entry(_sp, \
1659 &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \ 1669 &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \
@@ -4224,11 +4234,13 @@ restart:
4224 if (sp->role.invalid) 4234 if (sp->role.invalid)
4225 continue; 4235 continue;
4226 4236
4237 /*
4238 * Need not flush tlb since we only zap the sp with invalid
4239 * generation number.
4240 */
4227 if (batch >= BATCH_ZAP_PAGES && 4241 if (batch >= BATCH_ZAP_PAGES &&
4228 (need_resched() || spin_needbreak(&kvm->mmu_lock))) { 4242 cond_resched_lock(&kvm->mmu_lock)) {
4229 batch = 0; 4243 batch = 0;
4230 kvm_mmu_commit_zap_page(kvm, &invalid_list);
4231 cond_resched_lock(&kvm->mmu_lock);
4232 goto restart; 4244 goto restart;
4233 } 4245 }
4234 4246
@@ -4239,6 +4251,10 @@ restart:
4239 goto restart; 4251 goto restart;
4240 } 4252 }
4241 4253
4254 /*
4255 * Should flush tlb before free page tables since lockless-walking
4256 * may use the pages.
4257 */
4242 kvm_mmu_commit_zap_page(kvm, &invalid_list); 4258 kvm_mmu_commit_zap_page(kvm, &invalid_list);
4243} 4259}
4244 4260
@@ -4257,6 +4273,17 @@ void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm)
4257 trace_kvm_mmu_invalidate_zap_all_pages(kvm); 4273 trace_kvm_mmu_invalidate_zap_all_pages(kvm);
4258 kvm->arch.mmu_valid_gen++; 4274 kvm->arch.mmu_valid_gen++;
4259 4275
4276 /*
4277 * Notify all vcpus to reload its shadow page table
4278 * and flush TLB. Then all vcpus will switch to new
4279 * shadow page table with the new mmu_valid_gen.
4280 *
4281 * Note: we should do this under the protection of
4282 * mmu-lock, otherwise, vcpu would purge shadow page
4283 * but miss tlb flush.
4284 */
4285 kvm_reload_remote_mmus(kvm);
4286
4260 kvm_zap_obsolete_pages(kvm); 4287 kvm_zap_obsolete_pages(kvm);
4261 spin_unlock(&kvm->mmu_lock); 4288 spin_unlock(&kvm->mmu_lock);
4262} 4289}