KVM: MMU: Move kvm_free_some_pages() into critical section

If some other cpu steals mmu pages between our check and an attempt to
allocate, we can run out of mmu pages.  Fix by moving the check into the
same critical section as the allocation.

Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 834698d24595667d154a20110608e2e5f4be5b97..c478ee25de6606ddee52e11c88dd612cfc47b484 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -291,7 +291,6 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 {
        int r;
 
-       kvm_mmu_free_some_pages(vcpu);
        r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_chain_cache,
                                   pte_chain_cache, 4);
        if (r)
@@ -569,9 +568,6 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
 {
        struct kvm_mmu_page *sp;
 
-       if (!vcpu->kvm->arch.n_free_mmu_pages)
-               return NULL;
-
        sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache, sizeof *sp);
        sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache, PAGE_SIZE);
        sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache, PAGE_SIZE);
@@ -1024,6 +1020,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
        page = gfn_to_page(vcpu->kvm, gfn);
 
        spin_lock(&vcpu->kvm->mmu_lock);
+       kvm_mmu_free_some_pages(vcpu);
        r = __nonpaging_map(vcpu, v, write, gfn, page);
        spin_unlock(&vcpu->kvm->mmu_lock);
 
@@ -1275,6 +1272,7 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
        if (r)
                goto out;
        spin_lock(&vcpu->kvm->mmu_lock);
+       kvm_mmu_free_some_pages(vcpu);
        mmu_alloc_roots(vcpu);
        spin_unlock(&vcpu->kvm->mmu_lock);
        kvm_x86_ops->set_cr3(vcpu, vcpu->arch.mmu.root_hpa);
@@ -1413,6 +1411,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
        pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);
        mmu_guess_page_from_pte_write(vcpu, gpa, new, bytes);
        spin_lock(&vcpu->kvm->mmu_lock);
+       kvm_mmu_free_some_pages(vcpu);
        ++vcpu->kvm->stat.mmu_pte_write;
        kvm_mmu_audit(vcpu, "pre pte write");
        if (gfn == vcpu->arch.last_pt_write_gfn
@@ -1505,7 +1504,6 @@ int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
 
 void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
 {
-       spin_lock(&vcpu->kvm->mmu_lock);
        while (vcpu->kvm->arch.n_free_mmu_pages < KVM_REFILL_PAGES) {
                struct kvm_mmu_page *sp;
 
@@ -1514,7 +1512,6 @@ void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
                kvm_mmu_zap_page(vcpu->kvm, sp);
                ++vcpu->kvm->stat.mmu_recycled;
        }
-       spin_unlock(&vcpu->kvm->mmu_lock);
 }
 
 int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index a35b83a4fef2f25d681b236fc7b9133b13650e14..349920556be391bfd7911ff10ecaf9ce54273315 100644 (file)
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -402,6 +402,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
        page = gfn_to_page(vcpu->kvm, walker.gfn);
 
        spin_lock(&vcpu->kvm->mmu_lock);
+       kvm_mmu_free_some_pages(vcpu);
        shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
                                  &write_pt, page);
        pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __FUNCTION__,