[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] About block device mapping for guests
I am a bit puzzled on how the block device mapping works for Xen guests. Or particularily the fact on how the device shows on the guest side. When configuring the domain, one can specify the device name the partition should appear with inside the guest. And if that device does not exist on the host side, xend complains. A workaround for this was to specify the device with explicit minor and major number, instead of a name. So, from this I would conclude that you can specify the major and minor device number, which will map to the device you specify. Now, can these numbers be picked arbitrarily? I know I can mimic an entire disk (hda) or just a partition (hda1), for either IDE or SCSI - but is there any difference on the Xen side? Does Xen behave differently depending on the minor and major that I specify? Then, are the exported devices just plain block devices with nothing special to configure? I guess I can use the 'blockdev' command to change the blocksize and readahead size for the device? But do any special ioctl's or something like that pass through? If I export an entire hard disk, can the parameters for it tuned from inside the guest? What about CD/DVD/etc. drives? Do media insert notifications go through? Could I use a CD-burner from a guest? And yet more, how do these devices play along with devfs? Does the Xen blockdev frontend driver automatically create some nodes for devfs? Can it somehow make /dev/hda or /dev/sda appear on the guest side with devfs? How about udev? Does udev get boottime events to initialize the device nodes for the block devices? And what about sysfs? Is there a sysfs interface to see what has been mapped where and with what major and minor numbers? I've used to using UML, where devices ubd0 and onwards are UML block devices - they have their own major device number. They show up in devfs as /dev/ubd/disc0/disc, /dev/ubd/disc1/disc and so on. I think there was supposed to be a sysfs interface as well, but I'm not sure about that. So, how is this all handled in Xen? -- Naked ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/xen-devel
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