Re: [Qemu-stable] Data corruption in Qemu 2.7.1

[Paolo Bonzini]

On 17/01/2017 09:03, Fabian Grünbichler wrote:
> Commit 8fdc7839e40f43a426bc7e858cf1dbfe315a3804 (first included in
> 2.7.0)[1] changed the behaviour of scsi-block passthrough. Previously
> this worked with SATA disks, now it doesn't anymore. A bisect run
> confirmed this, scsi-block with a SATA disk passed through via
> virtio-scsi-single corrupts on writes since that commit, scsi-hd and
> scsi-disk work fine (scsi-generic corrupts as well).
> 
> PVE's detection logic for passthrough just differentiated between disks
> and tape drives, and unfortunately the SG_IO ioctl says SATA disks are
> disks as well.. we probably need to default to scsi-hd or scsi-disk
> instead of scsi-block, and only when we explicitly detect a "real" SCSI
> disk we are allowed to use scsi-block?
> 
> @Paolo: was the old behaviour just an accident and the new bevaviour
> intentional? documentation is quite sparse, or maybe I am looking in the
> wrong places..

No, it would be a bug (QEMU or kernel).

Do you have an easy reproducer with dd, as suggested at
https://forum.proxmox.com/threads/proxmox-4-4-virtio_scsi-regression.31471/page-2?

Paolo