On Tue, 01/17 14:17, Paolo Bonzini wrote: > > > On 16/01/2017 18:26, Fam Zheng wrote: > >> Is the endianness correct for big-endian host here? > > > > I think so. The fc_host sysfs uses u64 to represent port_name and node_name, > > this patch does the same, so using virtio_* helpers for these fields should > > handle the endianness correctly. > > I was suspicious about it because they are defined as "u8 x[8]" in the > virtio_scsi_config struct. So you would need to read with > virtio_cread_bytes and pass the result to wwn_to_u64. > > For example, if you have 0x500123456789abcd this would be > > 0x50 0x01 0x23 0x45 0x67 0x89 0xab 0cd > > in virtio_scsi_config, and then virtio_cread64 would read it as a > little-endian u64, 0xcdab896745230150. Maybe your QEMU patch is also > writing things as little-endian 64-bit integers, rather than 8-element > arrays of bytes? Yes, they all used 64-bit integers in a "less surprising" endian. I think there is an endianness conecpt to WWN, as in 0x500123456789abcd; and there is an native endianness to virtio, which is little-endian. If we use a "u8 x[8]" type in the spec and want the WWN's MSB, namely the 0x50 stuff, to be the first byte, is it worth to explicitly document that to avoid confusion? Fam -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
