Ping on this ... we've tripped the same issue on a different system, it would appear. Would appreciate if anyone can provide answers to the questions below.
Thanks, Nish On 15.05.2012 [10:01:41 -0700], Nishanth Aravamudan wrote: > Hi Santiago, > > Are you still working on ibmveth? > > I've found a very sporadic bug with ibmveth in some testing. PAPR > requires that: > > "Validate the Buffer Descriptor of the receive queue buffer (I/O > addresses for entire buffer length starting at the spec- ified I/O > address are translated by the RTCE table, length is a multiple of 16 > bytes, and alignment is on a 16 byte boundary) else H_Parameter." > > but from what I can tell ibmveth.c is not enforcing this last condition: > > adapter->rx_queue.queue_addr = > kmalloc(adapter->rx_queue.queue_len, GFP_KERNEL); > > ... > > adapter->rx_queue.queue_dma = dma_map_single(dev, > adapter->rx_queue.queue_addr, adapter->rx_queue.queue_len, > DMA_BIDIRECTIONAL); > > ... > > rxq_desc.fields.address = adapter->rx_queue.queue_dma; > > ... > > > lpar_rc = ibmveth_register_logical_lan(adapter, rxq_desc, > mac_address); > netdev_err(netdev, "buffer TCE:0x%llx filter TCE:0x%llx rxq " > "desc:0x%llx MAC:0x%llx\n", adapter->buffer_list_dma, > adapter->filter_list_dma, rxq_desc.desc, mac_address); > > And I got on one install attempt: > > [ 39.978430] ibmveth 30000004: eth0: h_register_logical_lan failed with -4 > [ 39.978449] ibmveth 30000004: eth0: buffer TCE:0x1000 filter TCE:0x10000 rxq > desc:0x80006010000200a8 MAC:0x56754de8e904 > > rxq desc, as you can see is not 16byte aligned. kmalloc() only > guarantees 8-byte alignment (as does gcc, I think). Initially, I thought > we could just overallocate the queue_addr and ALIGN() down, but then we > would need to save the original kmalloc pointer in a new struct member > per rx_queue. > > So a couple of questions: > > 1) Is my analysis accurate? :) > > 2) How gross would it be to save an extra pointer for every rx_queue? > > 3) Based upon 2), is it better to just go ahead and create our own > kmem_cache (which gets an alignment specified)? > > For 3), I started coding this, but couldn't find a clean place to > allocate the kmem_cache itself, as the size of each object depends on > the run-time characteristics (afaict), but needs to be specified at > cache creation time. Any insight you could provide would be great! > > Thanks, > Nish > > -- > Nishanth Aravamudan <n...@us.ibm.com> > IBM Linux Technology Center -- Nishanth Aravamudan <n...@us.ibm.com> IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
