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    Subject[patch 11/30] KVM: MMU: fix missing locking in alloc_mmu_pages
    2.6.30-stable review patch.  If anyone has any objections, please let us know.

    ------------------
    From: Marcelo Tosatti <mtosatti@redhat.com>

    (cherry picked from commit 6a1ac77110ee3e8d8dfdef8442f3b30b3d83e6a2)

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    arch/x86/kvm/mmu.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -2692,12 +2692,14 @@ static int alloc_mmu_pages(struct kvm_vc

    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



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