[PATCH v8 10/11] KVM: MMU: reclaim the zapped-obsolete page first
As Marcelo pointed out that
| "(retention of large number of pages while zapping)
| can be fatal, it can lead to OOM and host crash"
We introduce a list, kvm->arch.zapped_obsolete_pages, to link all
the pages which are deleted from the mmu cache but not actually
freed. When page reclaiming is needed, we always zap this kind of
pages first.
[
Can we use this list to instead all of "invalid_list"? That may
be interesting and will cause big change. Will do it separately
if it is necessary.
]
Signed-off-by: Xiao Guangrong
---
arch/x86/include/asm/kvm_host.h |2 ++
arch/x86/kvm/mmu.c | 21 +
arch/x86/kvm/x86.c |1 +
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bff7d46..1f98c1b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -536,6 +536,8 @@ struct kvm_arch {
* Hash table of struct kvm_mmu_page.
*/
struct list_head active_mmu_pages;
+ struct list_head zapped_obsolete_pages;
+
struct list_head assigned_dev_head;
struct iommu_domain *iommu_domain;
int iommu_flags;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 674c044..79af88a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4211,7 +4211,6 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
int slot)
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
- LIST_HEAD(invalid_list);
int batch = 0;
restart:
@@ -4244,7 +4243,8 @@ restart:
goto restart;
}
- ret = kvm_mmu_prepare_zap_page(kvm, sp, _list);
+ ret = kvm_mmu_prepare_zap_page(kvm, sp,
+ >arch.zapped_obsolete_pages);
batch += ret;
if (ret)
@@ -4255,7 +4255,7 @@ restart:
* Should flush tlb before free page tables since lockless-walking
* may use the pages.
*/
- kvm_mmu_commit_zap_page(kvm, _list);
+ kvm_mmu_commit_zap_page(kvm, >arch.zapped_obsolete_pages);
}
/*
@@ -4306,6 +4306,11 @@ restart:
spin_unlock(>mmu_lock);
}
+static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
+{
+ return unlikely(!list_empty_careful(>arch.zapped_obsolete_pages));
+}
+
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
{
struct kvm *kvm;
@@ -4334,15 +4339,23 @@ static int mmu_shrink(struct shrinker *shrink, struct
shrink_control *sc)
* want to shrink a VM that only started to populate its MMU
* anyway.
*/
- if (!kvm->arch.n_used_mmu_pages)
+ if (!kvm->arch.n_used_mmu_pages &&
+ !kvm_has_zapped_obsolete_pages(kvm))
continue;
idx = srcu_read_lock(>srcu);
spin_lock(>mmu_lock);
+ if (kvm_has_zapped_obsolete_pages(kvm)) {
+ kvm_mmu_commit_zap_page(kvm,
+ >arch.zapped_obsolete_pages);
+ goto unlock;
+ }
+
prepare_zap_oldest_mmu_page(kvm, _list);
kvm_mmu_commit_zap_page(kvm, _list);
+unlock:
spin_unlock(>mmu_lock);
srcu_read_unlock(>srcu, idx);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 15e10f7..6402951 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6832,6 +6832,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
return -EINVAL;
INIT_LIST_HEAD(>arch.active_mmu_pages);
+ INIT_LIST_HEAD(>arch.zapped_obsolete_pages);
INIT_LIST_HEAD(>arch.assigned_dev_head);
/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
--
1.7.7.6
--
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[PATCH v8 10/11] KVM: MMU: reclaim the zapped-obsolete page first
As Marcelo pointed out that
| (retention of large number of pages while zapping)
| can be fatal, it can lead to OOM and host crash
We introduce a list, kvm-arch.zapped_obsolete_pages, to link all
the pages which are deleted from the mmu cache but not actually
freed. When page reclaiming is needed, we always zap this kind of
pages first.
[
Can we use this list to instead all of invalid_list? That may
be interesting and will cause big change. Will do it separately
if it is necessary.
]
Signed-off-by: Xiao Guangrong xiaoguangr...@linux.vnet.ibm.com
---
arch/x86/include/asm/kvm_host.h |2 ++
arch/x86/kvm/mmu.c | 21 +
arch/x86/kvm/x86.c |1 +
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bff7d46..1f98c1b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -536,6 +536,8 @@ struct kvm_arch {
* Hash table of struct kvm_mmu_page.
*/
struct list_head active_mmu_pages;
+ struct list_head zapped_obsolete_pages;
+
struct list_head assigned_dev_head;
struct iommu_domain *iommu_domain;
int iommu_flags;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 674c044..79af88a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4211,7 +4211,6 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
int slot)
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
- LIST_HEAD(invalid_list);
int batch = 0;
restart:
@@ -4244,7 +4243,8 @@ restart:
goto restart;
}
- ret = kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
+ ret = kvm_mmu_prepare_zap_page(kvm, sp,
+ kvm-arch.zapped_obsolete_pages);
batch += ret;
if (ret)
@@ -4255,7 +4255,7 @@ restart:
* Should flush tlb before free page tables since lockless-walking
* may use the pages.
*/
- kvm_mmu_commit_zap_page(kvm, invalid_list);
+ kvm_mmu_commit_zap_page(kvm, kvm-arch.zapped_obsolete_pages);
}
/*
@@ -4306,6 +4306,11 @@ restart:
spin_unlock(kvm-mmu_lock);
}
+static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
+{
+ return unlikely(!list_empty_careful(kvm-arch.zapped_obsolete_pages));
+}
+
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
{
struct kvm *kvm;
@@ -4334,15 +4339,23 @@ static int mmu_shrink(struct shrinker *shrink, struct
shrink_control *sc)
* want to shrink a VM that only started to populate its MMU
* anyway.
*/
- if (!kvm-arch.n_used_mmu_pages)
+ if (!kvm-arch.n_used_mmu_pages
+ !kvm_has_zapped_obsolete_pages(kvm))
continue;
idx = srcu_read_lock(kvm-srcu);
spin_lock(kvm-mmu_lock);
+ if (kvm_has_zapped_obsolete_pages(kvm)) {
+ kvm_mmu_commit_zap_page(kvm,
+ kvm-arch.zapped_obsolete_pages);
+ goto unlock;
+ }
+
prepare_zap_oldest_mmu_page(kvm, invalid_list);
kvm_mmu_commit_zap_page(kvm, invalid_list);
+unlock:
spin_unlock(kvm-mmu_lock);
srcu_read_unlock(kvm-srcu, idx);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 15e10f7..6402951 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6832,6 +6832,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
return -EINVAL;
INIT_LIST_HEAD(kvm-arch.active_mmu_pages);
+ INIT_LIST_HEAD(kvm-arch.zapped_obsolete_pages);
INIT_LIST_HEAD(kvm-arch.assigned_dev_head);
/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
--
1.7.7.6
--
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