On 2016/02/15 16:52, Tan, Jianfeng wrote: > Hi Tetsuya, > > On 2/10/2016 11:40 AM, Tetsuya Mukawa wrote: >> To work with qtest virtio-net PMD, virtual address that maps hugepages >> should be between (1 << 31) to (1 << 44). This patch adds one more >> option > > Is there any reference about this limitation? And is it also true for > 32 bit machine? >
Hi Jianfeng, 44bit limitation is come from virtio legacy device spec. The queue address register of virtio device is 32bit width. And we should set page number to this register. As a result, EAL memory should be under 44 bits. I only support virtio modern device with this patch series. So we can relax this limitation a bit. (Next limitation may be 47 bits. It seems it is come from QEMU implementation.) But I guess 44bit limitation is still not so hard, also we can leave a possibility to support legacy device. 31bits limitation is come from current memory mapping of QTest QEMU guest. Here is. * ------------------------------------------------------------ * Memory mapping of qtest quest * ------------------------------------------------------------ * 0x00000000_00000000 - 0x00000000_3fffffff : not used * 0x00000000_40000000 - 0x00000000_40000fff : virtio-net(BAR1) * 0x00000000_40001000 - 0x00000000_40ffffff : not used * 0x00000000_41000000 - 0x00000000_417fffff : virtio-net(BAR4) * 0x00000000_41800000 - 0x00000000_41ffffff : not used * 0x00000000_42000000 - 0x00000000_420000ff : ivshmem(BAR0) * 0x00000000_42000100 - 0x00000000_42ffffff : not used * 0x00000000_80000000 - 0xffffffff_ffffffff : ivshmem(BAR2) Thanks, Tetsuya > Thanks, > Jianfeng