linux-kernel - [193/200] KVM: MMU: Dont read pdptrs with mmu spinlock held in mmu_alloc

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Message-Id: <20100701174302.814231455@clark.site>
Date:	Thu, 01 Jul 2010 10:44:43 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Avi Kivity <avi@...hat.com>
Subject: [193/200] KVM: MMU: Dont read pdptrs with mmu spinlock held in mmu_alloc_roots

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Avi Kivity <avi@...hat.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.

Tested-by: Joerg Roedel <joerg.roedel@....com>
Signed-off-by: Avi Kivity <avi@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

(Cherry-picked from commit 8facbbff071ff2b19268d3732e31badc60471e21)
---
 arch/x86/kvm/mmu.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2085,11 +2085,13 @@ static int mmu_alloc_roots(struct kvm_vc
 			direct = 1;
 		if (mmu_check_root(vcpu, root_gfn))
 			return 1;
+		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;
 	}
@@ -2111,11 +2113,14 @@ static int mmu_alloc_roots(struct kvm_vc
 			root_gfn = 0;
 		if (mmu_check_root(vcpu, root_gfn))
 			return 1;
+		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);
@@ -2479,7 +2484,9 @@ 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)


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