[PATCH 089/104] KVM: MMU: Don't do GFP_NOWAIT allocations

Avi Kivity
2007-09-17T08:32:11Z

Before preempt notifiers, kvm needed to allocate memory with GFP_NOWAIT so
as not to have to enable preemption and take a heavyweight exit. On oom, we'd
fall back to a GFP_KERNEL allocation.

With preemption notifiers, we can do a GFP_KERNEL allocation, and perform
the heavyweight exit only if the kernel decides to put us to sleep.

Signed-off-by: Avi Kivity <avi@qumranet.com>
---
drivers/kvm/mmu.c | 34 ++++++++++------------------------
1 files changed, 10 insertions(+), 24 deletions(-)

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 7b42c88..6d84d30 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -202,15 +202,14 @@ static void set_shadow_pte(u64 *sptep, u64 spte)
}

static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
- struct kmem_cache *base_cache, int min,
- gfp_t gfp_flags)
+ struct kmem_cache *base_cache, int min)
{
void *obj;

if (cache->nobjs >= min)
return 0;
while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
- obj = kmem_cache_zalloc(base_cache, gfp_flags);
+ obj = kmem_cache_zalloc(base_cache, GFP_KERNEL);
if (!obj)
return -ENOMEM;
cache->objects[cache->nobjs++] = obj;
@@ -225,14 +224,14 @@ static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
}

static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache,
- int min, gfp_t gfp_flags)
+ int min)
{
struct page *page;

if (cache->nobjs >= min)
return 0;
while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
- page = alloc_page(gfp_flags);
+ page = alloc_page(GFP_KERNEL);
if (!page)
return -ENOMEM;
set_page_private(page, 0);
@@ -247,41 +246,28 @@ static void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc)
free_page((unsigned long)mc->objects[--mc->nobjs]);
}

-static int __mmu_topup_memory_caches(struct kvm_vcpu *vcpu, gfp_t gfp_flags)
+static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
{
int r;

+ kvm_mmu_free_some_pages(vcpu);
r = mmu_topup_memory_cache(&vcpu->mmu_pte_chain_cache,
- pte_chain_cache, 4, gfp_flags);
+ pte_chain_cache, 4);
if (r)
goto out;
r = mmu_topup_memory_cache(&vcpu->mmu_rmap_desc_cache,
- rmap_desc_cache, 1, gfp_flags);
+ rmap_desc_cache, 1);
if (r)
goto out;
- r = mmu_topup_memory_cache_page(&vcpu->mmu_page_cache, 4, gfp_flags);
+ r = mmu_topup_memory_cache_page(&vcpu->mmu_page_cache, 4);
if (r)
goto out;
r = mmu_topup_memory_cache(&vcpu->mmu_page_header_cache,
- mmu_page_header_cache, 4, gfp_flags);
+ mmu_page_header_cache, 4);
out:
return r;
}

-static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
-{
- int r;
-
- r = __mmu_topup_memory_caches(vcpu, GFP_NOWAIT);
- kvm_mmu_free_some_pages(vcpu);
- if (r < 0) {
- mutex_unlock(&vcpu->kvm->lock);
- r = __mmu_topup_memory_caches(vcpu, GFP_KERNEL);
- mutex_lock(&vcpu->kvm->lock);
- }
- return r;
-}
-
static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
mmu_free_memory_cache(&vcpu->mmu_pte_chain_cache);
--
1.5.3