Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965356Ab3IEKdo (ORCPT ); Thu, 5 Sep 2013 06:33:44 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:33947 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935607Ab3IEK3m (ORCPT ); Thu, 5 Sep 2013 06:29:42 -0400 From: Xiao Guangrong To: gleb@redhat.com Cc: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Xiao Guangrong Subject: [PATCH v2 05/15] KVM: MMU: flush tlb out of mmu lock when write-protect the sptes Date: Thu, 5 Sep 2013 18:29:08 +0800 Message-Id: <1378376958-27252-6-git-send-email-xiaoguangrong@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1378376958-27252-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> References: <1378376958-27252-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13090510-9574-0000-0000-0000097E082A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2960 Lines: 83 Now we can flush all the TLBs out of the mmu lock without TLB corruption when write-proect the sptes, it is because: - we have marked large sptes readonly instead of dropping them that means we just change the spte from writable to readonly so that we only need to care the case of changing spte from present to present (changing the spte from present to nonpresent will flush all the TLBs immediately), in other words, the only case we need to care is mmu_spte_update() - in mmu_spte_update(), we have checked SPTE_HOST_WRITEABLE | PTE_MMU_WRITEABLE instead of PT_WRITABLE_MASK, that means it does not depend on PT_WRITABLE_MASK anymore Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 18 ++++++++++++++---- arch/x86/kvm/x86.c | 9 +++++++-- 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 7488229..a983570 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4320,15 +4320,25 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) if (*rmapp) __rmap_write_protect(kvm, rmapp, false); - if (need_resched() || spin_needbreak(&kvm->mmu_lock)) { - kvm_flush_remote_tlbs(kvm); + if (need_resched() || spin_needbreak(&kvm->mmu_lock)) cond_resched_lock(&kvm->mmu_lock); - } } } - kvm_flush_remote_tlbs(kvm); spin_unlock(&kvm->mmu_lock); + + /* + * We can flush all the TLBs out of the mmu lock without TLB + * corruption since we just change the spte from writable to + * readonly so that we only need to care the case of changing + * spte from present to present (changing the spte from present + * to nonpresent will flush all the TLBs immediately), in other + * words, the only case we care is mmu_spte_update() where we + * haved checked SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE + * instead of PT_WRITABLE_MASK, that means it does not depend + * on PT_WRITABLE_MASK anymore. + */ + kvm_flush_remote_tlbs(kvm); } #define BATCH_ZAP_PAGES 10 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6ad0c07..72f1487 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3560,11 +3560,16 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log) offset = i * BITS_PER_LONG; kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, mask); } - if (is_dirty) - kvm_flush_remote_tlbs(kvm); spin_unlock(&kvm->mmu_lock); + /* + * All the TLBs can be flushed out of mmu lock, see the comments in + * kvm_mmu_slot_remove_write_access(). + */ + if (is_dirty) + kvm_flush_remote_tlbs(kvm); + r = -EFAULT; if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n)) goto out; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/