From: Marcelo Tosatti <mtosatti@redhat.com>
To: kvm@vger.kernel.org
Subject: KVM: MMU: fix missing locking in alloc_mmu_pages
Date: Wed, 15 Jul 2009 15:34:41 -0300 [thread overview]
Message-ID: <20090715183441.GA8402@amt.cnet> (raw)
n_requested_mmu_pages/n_free_mmu_pages are used by
kvm_mmu_change_mmu_pages to calculate the number of pages to zap.
alloc_mmu_pages, called from the vcpu initialization path, modifies this
variables without proper locking, which can result in a negative value
in kvm_mmu_change_mmu_pages (say, with cpu hotplug).
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 7162651..6773d49 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2704,12 +2704,14 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
ASSERT(vcpu);
+ spin_lock(&vcpu->kvm->mmu_lock);
if (vcpu->kvm->arch.n_requested_mmu_pages)
vcpu->kvm->arch.n_free_mmu_pages =
vcpu->kvm->arch.n_requested_mmu_pages;
else
vcpu->kvm->arch.n_free_mmu_pages =
vcpu->kvm->arch.n_alloc_mmu_pages;
+ spin_unlock(&vcpu->kvm->mmu_lock);
/*
* When emulating 32-bit mode, cr3 is only 32 bits even on x86_64.
* Therefore we need to allocate shadow page tables in the first
reply other threads:[~2009-07-15 18:34 UTC|newest]
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