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Revert "KVM: MMU: zap pages in batch"

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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 e7d11c7a89.

[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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-02-05 13:01:28 -08:00 committed by Paolo Bonzini
parent 210f494261
commit 43d2b14b10
1 changed files with 24 additions and 11 deletions
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35
arch/x86/kvm/mmu.c
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@ -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 @@ restart:
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 @@ restart:
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;
}