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    Subject[PATCH 3.12 068/133] KVM: s390: ioeventfd: ignore leftmost bits
    Date
    3.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Dominik Dingel <dingel@linux.vnet.ibm.com>

    commit ff1f3cb4b3ac5d039f02679f34cb1498d110d241 upstream.

    The diagnose 500 subcode 3 contains the 32 bit subchannel id in bits 32-63
    (counting from the left). As for other I/O instructions, bits 0-31 should be
    ignored and thus not be passed to kvm_io_bus_write_cookie().

    This fixes a bug where the guest passed non-zero bits 0-31 which the
    host tried to interpret, leading to ioeventfd notification failures.

    Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
    Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
    Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/s390/kvm/diag.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/arch/s390/kvm/diag.c
    +++ b/arch/s390/kvm/diag.c
    @@ -122,7 +122,7 @@ static int __diag_virtio_hypercall(struc
    * - gpr 4 contains the index on the bus (optionally)
    */
    ret = kvm_io_bus_write_cookie(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
    - vcpu->run->s.regs.gprs[2],
    + vcpu->run->s.regs.gprs[2] & 0xffffffff,
    8, &vcpu->run->s.regs.gprs[3],
    vcpu->run->s.regs.gprs[4]);
    srcu_read_unlock(&vcpu->kvm->srcu, idx);



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