Hi, > Can there be a guest that will fail the MBR in such a way? Yes. > Look at the following MBR partition table of a Windows XP guest in our > production > environment: > > Disk size in sectors: 16777216 > > Binary (only one partition 16 bytes): 80 01 01 00 07 fe ff ff 3f 00 00 00 d5 > ea ff 00 > Start: (0, 1, 1, 63) > End: (1023, 254, 63, 16771859) > > As can be easily seen, any MBR guessing algorithm should guess: > > 255 heads (since a value of 254 appears), 63 spt (since a value of 63 > appears) > > Turns out that this image does not work with 255, 63 but actually requires > > 16 heads, 63 spt > > to boot. > > So relying on MBR partitions alone is not always enough and sometimes manual > intervention > is required.
Ok, given that seabios has no setup any manual configuration needs to be done via qemu. But why do we need a new interface for that? IDE can pass the geometry to the guest. virtio-blk has support too (VIRTIO_BLK_F_GEOMETRY). Likewise scsi (MODE_PAGE_HD_GEOMETRY). So this should be doable without any qemu changes. cheers, Gerd