On 2012-05-28 16:06, Avi Kivity wrote: > On 05/28/2012 04:03 PM, Jan Kiszka wrote: >> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >> >> If the kernel does not support ioport access via sysfs, passthrough can >> only help if the unlikely case that a port <= 0x3ff is provided by the >> device. So drop this to simplify the code and to allow dropping the >> corresponding KVM infrastructure in preparation of upstream merge. >> >> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >> --- >> >> Does anyone recall the precise use case this was introduced for? It >> exists since day #1, so commit logs do not help. > > At a wild guess, graphics device assignment. The only explanation now. But that requires more work anyway (e.g. to claim the VGA adapter toward the kernel). And I but we would rather do this on top of VFIO on day. > > Under what conditions would the kernel not support ioport access via sysfs? > No clue. The oldest kernel I checked (2.6.16) does not contain traces it would refuse to provide access. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
