[0/2] block;scsi-generic: Fix max transfer size calculation

Message

Dmitry Fomichev Aug. 11, 2020, 10:51 p.m. UTC

When a host-managed zoned device is passed through to the
guest system using scsi-generic driver, the maximum i/o size for the
drive at the guest may end up being larger than at the host, causing
i/o errors while accessing the backing zoned drive at the host system.

Two problems prevent correct setting of the maximum i/o transfer size
at the guest in this configuration. One issue is specific to
host-managed zone devices - scsi-generic driver doesn't recognize the
SCSI type of HM-zoned devices. The other problem is that file-posix
code for finding max_segments system value doesn't correctly handle
SG nodes.

The following two patches fix these problems.

Based-on: <[e-mail]>

Dmitry Fomichev (2):
  file-posix: Correctly read max_segments of SG nodes
  scsi-generic: Fix HM-zoned device scan

 block/file-posix.c       | 55 +++++++++++++++++++++++-----------------
 hw/scsi/scsi-generic.c   | 10 +++++---
 include/scsi/constants.h |  1 +
 3 files changed, 39 insertions(+), 27 deletions(-)

Comments

Paolo Bonzini Aug. 17, 2020, 4:38 p.m. UTC | #1

On 12/08/20 00:51, Dmitry Fomichev wrote:
> When a host-managed zoned device is passed through to the
> guest system using scsi-generic driver, the maximum i/o size for the
> drive at the guest may end up being larger than at the host, causing
> i/o errors while accessing the backing zoned drive at the host system.
> 
> Two problems prevent correct setting of the maximum i/o transfer size
> at the guest in this configuration. One issue is specific to
> host-managed zone devices - scsi-generic driver doesn't recognize the
> SCSI type of HM-zoned devices. The other problem is that file-posix
> code for finding max_segments system value doesn't correctly handle
> SG nodes.
> 
> The following two patches fix these problems.
> 
> Based-on: <[e-mail]>
> 
> Dmitry Fomichev (2):
>   file-posix: Correctly read max_segments of SG nodes
>   scsi-generic: Fix HM-zoned device scan
> 
>  block/file-posix.c       | 55 +++++++++++++++++++++++-----------------
>  hw/scsi/scsi-generic.c   | 10 +++++---
>  include/scsi/constants.h |  1 +
>  3 files changed, 39 insertions(+), 27 deletions(-)
> 

The patches are more or less unrelated; I have queued the second, while
the first is outside my maintenance area.

Paolo