KVM: MMU: Don't do GFP_NOWAIT allocations

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>

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 7b42c88..6d84d30 100644 (file)
--- 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);