Enabling KVM with recent QEMU builds from GIT hang at boot on Ubuntu Precise AMD64 kernel 3.8.0

When I compile QEMU from GIT and run it with './x86_64-softmmu/qemu-system-x86_64 -enable-kvm' it just hangs, the QEMU screen stays black. (Everything else in the GTK UI is responsive though, I can use the QEMU console as well.)
I'm running Ubuntu Precise with kernel 3.8.0-27-generic on an Intel Core2 Duo P9500.

With bisecting, I found this commit caused the problem:

235e8982ad393e5611cb892df54881c872eea9e1 is the first bad commit
commit 235e8982ad393e5611cb892df54881c872eea9e1
Author: Jordan Justen <email address hidden>
Date:   Wed May 29 01:27:26 2013 -0700

    kvm: support using KVM_MEM_READONLY flag for regions

    For readonly memory regions and rom devices in romd_mode,
    we make use of the KVM_MEM_READONLY. A slot that uses
    KVM_MEM_READONLY can be read from and code can execute from the
    region, but writes will exit to qemu.

    For rom devices with !romd_mode, we force the slot to be
    removed so reads or writes to the region will exit to qemu.
    (Note that a memory region in this state is not executable
    within kvm.)

    v7:
     * Update for readable => romd_mode rename (5f9a5ea1)

    Signed-off-by: Jordan Justen <email address hidden>
    Reviewed-by: Xiao Guangrong <email address hidden> (v4)
    Reviewed-by: Paolo Bonzini <email address hidden> (v5)
    Message-id: <email address hidden>
    Signed-off-by: Anthony Liguori <email address hidden>

:100644 100644 327ae12f08b9dddc796d753d8adfb1f70c78b2c1 8e7bbf8698f6bcaa5ae945ef86e7b51effde06fe M      kvm-all.c