[PATCH] KVM: MMU: Don't read pdptrs with mmu spinlock held in mmu_alloc_roots

[Avi Kivity <avi@redhat.com>]

On svm, kvm_read_pdptr() may require reading guest memory, which can sleep.

Push the spinlock into mmu_alloc_roots(), and only take it after we've read
the pdptr.

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

Marcelo, dropping and re-acquiring the lock before mmu_sync_roots(), is fine,
yes?

 arch/x86/kvm/mmu.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 51eb6d6..de99638 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2065,11 +2065,13 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
 			direct = 1;
 			root_gfn = 0;
 		}
+		spin_lock(&vcpu->kvm->mmu_lock);
 		sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
 				      PT64_ROOT_LEVEL, direct,
 				      ACC_ALL, NULL);
 		root = __pa(sp->spt);
 		++sp->root_count;
+		spin_unlock(&vcpu->kvm->mmu_lock);
 		vcpu->arch.mmu.root_hpa = root;
 		return 0;
 	}
@@ -2093,11 +2095,14 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
 			direct = 1;
 			root_gfn = i << 30;
 		}
+		spin_lock(&vcpu->kvm->mmu_lock);
 		sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
 				      PT32_ROOT_LEVEL, direct,
 				      ACC_ALL, NULL);
 		root = __pa(sp->spt);
 		++sp->root_count;
+		spin_unlock(&vcpu->kvm->mmu_lock);
+
 		vcpu->arch.mmu.pae_root[i] = root | PT_PRESENT_MASK;
 	}
 	vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.pae_root);
@@ -2466,7 +2471,9 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
 		goto out;
 	spin_lock(&vcpu->kvm->mmu_lock);
 	kvm_mmu_free_some_pages(vcpu);
+	spin_unlock(&vcpu->kvm->mmu_lock);
 	r = mmu_alloc_roots(vcpu);
+	spin_lock(&vcpu->kvm->mmu_lock);
 	mmu_sync_roots(vcpu);
 	spin_unlock(&vcpu->kvm->mmu_lock);
 	if (r)
-- 
1.7.0.4