Commit 2e3e5882 authored by Avi Kivity's avatar Avi Kivity
Browse files

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: default avatarAvi Kivity <avi@qumranet.com>
parent cbdd1bea

drivers/kvm/mmu.c

+10 −24
Original line number Diff line number Diff line
@@ -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);

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