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KVM: MMU: fix missing locking in alloc_mmu_pages

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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>
This commit is contained in:
Marcelo Tosatti 2009-07-15 15:34:41 -03:00 committed by Avi Kivity
parent 3662cb1cd6
commit 6a1ac77110
1 changed files with 2 additions and 0 deletions
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2
arch/x86/kvm/mmu.c
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@ -2728,12 +2728,14 @@ 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