@@ -5843,18 +5843,14 @@ void kvm_mmu_slot_set_dirty(struct kvm *kvm,
}
EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty);
-#define BATCH_ZAP_PAGES 10
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
LIST_HEAD(invalid_list);
- int batch = 0;
restart:
list_for_each_entry_safe_reverse(sp, node,
&kvm->arch.active_mmu_pages, link) {
- int ret;
-
/*
* No obsolete page exists before new created page since
* active_mmu_pages is the FIFO list.
@@ -5863,6 +5859,28 @@ static void kvm_zap_obsolete_pages(struct kvm *kvm)
break;
/*
+ * Do not repeatedly zap a root page to avoid unnecessary
+ * KVM_REQ_MMU_RELOAD, otherwise we may not be able to
+ * progress:
+ * vcpu 0 vcpu 1
+ * call vcpu_enter_guest():
+ * 1): handle KVM_REQ_MMU_RELOAD
+ * and require mmu-lock to
+ * load mmu
+ * repeat:
+ * 1): zap root page and
+ * send KVM_REQ_MMU_RELOAD
+ *
+ * 2): if (cond_resched_lock(mmu-lock))
+ *
+ * 2): hold mmu-lock and load mmu
+ *
+ * 3): see KVM_REQ_MMU_RELOAD bit
+ * on vcpu->requests is set
+ * then return 1 to call
+ * vcpu_enter_guest() again.
+ * goto repeat;
+ *
* Since we are reversely walking the list and the invalid
* list will be moved to the head, skip the invalid page
* can help us to avoid the infinity list walking.
@@ -5870,18 +5888,13 @@ static void kvm_zap_obsolete_pages(struct kvm *kvm)
if (sp->role.invalid)
continue;
- if (batch >= BATCH_ZAP_PAGES &&
- (need_resched() || spin_needbreak(&kvm->mmu_lock))) {
- batch = 0;
+ if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
kvm_mmu_commit_zap_page(kvm, &invalid_list);
cond_resched_lock(&kvm->mmu_lock);
goto restart;
}
- ret = kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
- batch += ret;
-
- if (ret)
+ if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
goto restart;
}
Unwinding optimizations related to obsolete pages is a step towards removing x86 KVM's fast invalidate mechanism, i.e. this is one part of a revert all patches from the series that introduced the mechanism[1]. This reverts commit e7d11c7a894986a13817c1c001e1e7668c5c4eb4. [1] https://lkml.kernel.org/r/1369960590-14138-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com Cc: Xiao Guangrong <guangrong.xiao@gmail.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/mmu.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-)