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Subject[PATCH v4 6/6] KVM: MMU: make kvm_mmu_zap_all preemptable
Date
Now, kvm_mmu_zap_all is only called in the path of mmu_notifier->release,
at that time, vcpu has stopped that means no new page will be create, we
can use lock-break technique to avoid potential soft lockup

(Note: at this time, the mmu-lock still has contention between ->release
and other mmu-notify handlers.)

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
arch/x86/kvm/mmu.c | 11 ++++++++++-
1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 63110c7..46d1d47 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4197,12 +4197,21 @@ void kvm_mmu_zap_all(struct kvm *kvm)
struct kvm_mmu_page *sp, *node;
LIST_HEAD(invalid_list);

+ might_sleep();
+
spin_lock(&kvm->mmu_lock);
restart:
- list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link)
+ list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
goto restart;

+ if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
+ kvm_mmu_commit_zap_page(kvm, &invalid_list);
+ cond_resched_lock(&kvm->mmu_lock);
+ goto restart;
+ }
+ }
+
kvm_mmu_commit_zap_page(kvm, &invalid_list);
spin_unlock(&kvm->mmu_lock);
}
--
1.7.7.6


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