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    Subject[PATCH 31/31] KVM: MMU: kvm_pv_mmu_op should not take mmap_sem
    Date
    From: Marcelo Tosatti <mtosatti@redhat.com>

    kvm_pv_mmu_op should not take mmap_sem. All gfn_to_page() callers down
    in the MMU processing will take it if necessary, so as it is it can
    deadlock.

    Apparently a leftover from the days before slots_lock.

    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    Signed-off-by: Avi Kivity <avi@qumranet.com>
    ---
    arch/x86/kvm/mmu.c | 3 ---
    1 files changed, 0 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index 078a7f1..2ad6f54 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -2173,8 +2173,6 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
    int r;
    struct kvm_pv_mmu_op_buffer buffer;

    - down_read(&current->mm->mmap_sem);
    -
    buffer.ptr = buffer.buf;
    buffer.len = min_t(unsigned long, bytes, sizeof buffer.buf);
    buffer.processed = 0;
    @@ -2194,7 +2192,6 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
    r = 1;
    out:
    *ret = buffer.processed;
    - up_read(&current->mm->mmap_sem);
    return r;
    }

    --
    1.5.5


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