[Qemu-devel] [RFC PATCH 0/9] scsi: support s/g operation without a bounce buffer

[Paolo Bonzini <pbonzini@redhat.com>]

This is the third part in my SCSI s/g series.  From quick benchmarking,
it speeds up some workloads by 2-4 times.  Benefits vary depending on
the number of sectors read/written by the typical operation.  More precise
numbers of course will come.

Unlike the previous attempts, which forced devices to use an iovec
provided by the HBA, here the devices can choose whether to use the
old mechanism or the iovecs.  In addition, I do not plan to add this
to real devices, only paravirtual.  For this reason, this series includes
an emulation of the vmware pvscsi device (the emulation is complete
except for hotplug and PIO operation, both of which are undocumented
AFAICS).

The series currently depends on the cpu_physical_memory_fast operations.
The dependency can be removed if necessary though.  In fact, I would like
an overall comment on the API since I might as well drop pvscsi completely
and just implement this for virtio-scsi.

Paolo Bonzini (9):
  make qbus_reset_all public
  pvscsi: first commit
  pvscsi: check validity of DMA addresses in advance
  scsi: always use get_sense
  scsi-disk: lazily allocate bounce buffer
  allow switching a qiov between internal and external storage
  scsi: push qiov to SCSIRequest
  scsi: add get_iovec to SCSIBusOps
  pvscsi: implement s/g operation without a bounce buffer

 Makefile.objs           |    1 +
 cutils.c                |   14 +-
 default-configs/pci.mak |    1 +
 hw/pci.h                |    1 +
 hw/qdev.c               |    7 +-
 hw/qdev.h               |    2 +-
 hw/scsi-bus.c           |   20 +-
 hw/scsi-disk.c          |   62 ++-
 hw/scsi.h               |    4 +
 hw/spapr_vscsi.c        |   90 +----
 hw/vmw_pvscsi.c         | 1014 +++++++++++++++++++++++++++++++++++++++++++++++
 hw/vmw_pvscsi.h         |  389 ++++++++++++++++++
 trace-events            |   15 +
 vl.c                    |    2 +-
 14 files changed, 1518 insertions(+), 104 deletions(-)
 create mode 100644 hw/vmw_pvscsi.c
 create mode 100644 hw/vmw_pvscsi.h

-- 
1.7.4.4