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Commit 43d2b14b authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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Revert "KVM: MMU: zap pages in batch" 

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 e7d11c7a.

[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: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 210f4942

arch/x86/kvm/mmu.c

+24 −11
Original line number Diff line number Diff line
@@ -5846,18 +5846,14 @@ 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.
@@ -5866,6 +5862,28 @@ 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.
@@ -5873,18 +5891,13 @@ 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;

	}