On Tue, Feb 14, 2012 at 10:30:59AM +1100, ronnie sahlberg wrote: > On Tue, Feb 14, 2012 at 9:59 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > On Tue, Feb 14, 2012 at 07:53:26AM +1100, ronnie sahlberg wrote: > >> On Tue, Feb 14, 2012 at 7:42 AM, ronnie sahlberg > >> <ronniesahlberg@xxxxxxxxx> wrote: > >> > On Tue, Feb 14, 2012 at 2:12 AM, Hannes Reinecke <hare@xxxxxxx> wrote: > >> >> On 02/13/2012 02:18 PM, Michael S. Tsirkin wrote: > >> >>> On Tue, Feb 14, 2012 at 12:13:36AM +1100, ronnie sahlberg wrote: > >> >>>> On Tue, Feb 14, 2012 at 12:00 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > >> >>>>> On Mon, Feb 13, 2012 at 02:54:03PM +0200, Dor Laor wrote: > >> >>>>>> Only if you use the pci multi-function option but that kills > >> >>>>>> standard hot unplug > >> >>>>> > >> >>>>> It doesn't kill it as such, rather you can't unplug luns individually. > >> >>>> > >> >>>> Isnt that just a consequence of the current implementation rather than > >> >>>> a SCSI limitation? > >> >>> > >> >>> Yes. > >> >>> > >> >>>> A different way to do hoplug could be to flag all devices as removable > >> >>>> in the standard inq page then > >> >>>> leave the LUN there persistently and what you remove/add is not the > >> >>>> LUN device itself but just the media in the device. > >> >>>> > >> >>>> Instead of hot-plug remove the LUN, hot-plug becomes "media eject" or > >> >>>> "media insert". > >> >>>> The device remains present all time, you never remove it, but instead > >> >>>> hot-plug controls if the media is present or not. > >> >>>> > >> >>>> > >> >>>> This would require implementing at least START_STOP_UNIT and > >> >>>> PREVENT_ALLOW_MEDIUM_REMOVAL opcode emulation from SBC. > >> >>>> > >> >>>> > >> >>>> regards > >> >>>> ronnie sahlberg > >> >>> > >> >>> That would work. > >> >>> > >> >> Or we simply use the Peripheral Qualifier that the device is gone; > >> >> eg we could simply set PQ = 1, return sense code 0x25/00 and be done > >> >> with ... > >> >> > >> > > >> > That is still similar to "rip a device out from the guest without notice" > >> > and can cause the guest to be "surprised". > >> > > >> > > >> > Removable media is standard feature in SCSI SBC (and other commandsets). > >> > The nice part of removable media is that it activates a contract > >> > between the device and the guest > >> > to prevent removal of the media when the guest depends on the media > >> > not being removed. > >> > > >> > I.e. If you have a SBC device with the removable-media bit set, > >> > this is used to tell the initiator "this media can be removed, be > >> > prepared that this might happen". > >> > So when you mount such a SBC device in the guest, the guest will issue > >> > a "PREVENT_ALLOW_MEDIUM_REMOVAL" > >> > to tell the device "this medium is in use and may not be removed". > >> > > >> > >> What I mean is that if /dev/sdb is removable, > >> if you mount this as "mount /dev/sdb1 /mnt" > >> this will automatically cause the guest kernel to send a > >> PREVENT_ALLOW_MEDIUM_REMOVAL to /dev/sdb to prevent removal. > >> > >> When you "umount /dev/sdb1" the kernel/guest will automagically send > >> PREVENT_ALLOW_MEDIUM_REMOVEAL to /dev/sdb and allow removal of the > >> media again. > >> > >> > >> If you capture this command and track the "prevent/allow removal > >> status" you automatically get a channel where qemu will > >> know when it is safe to unplug the device and when it is not safe to > >> unplug the device. > >> This is a nice feature. > > > > Presumably there's a way for device to notify the OS > > that user requested removal, as well? > > > I think that is done by responding with sense to one of the commands, > like the every few second TEST_UNIT_READY that the > initiator/guest-kernel will send. Does it do this even for mounted media? I didn't realize ... -- 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
