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Re: [Qemu-devel] [PATCH 4/7] scsi-disk: introduce dma_readv and dma_writ

From: xiaoqiang zhao
Subject: Re: [Qemu-devel] [PATCH 4/7] scsi-disk: introduce dma_readv and dma_writev
Date: Fri, 3 Jun 2016 14:07:14 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

在 2016年06月03日 13:22, Mark Cave-Ayland 写道:
On 03/06/16 03:56, xiaoqiang zhao wrote:

在 2016年06月02日 03:07, Mark Cave-Ayland 写道:
On 23/05/16 13:54, Paolo Bonzini wrote:

These are replacements for blk_aio_preadv and blk_aio_pwritev that
customization of the data path.  They reuse the DMA helpers' DMAIOFunc
callback type, so that the same function can be used in either the
QEMUSGList or the bounce-buffered case.

This customization will be needed in the next patch to do zero-copy
SG_IO on scsi-block.

Signed-off-by: Paolo Bonzini<address@hidden>
  hw/scsi/scsi-disk.c | 63
  1 file changed, 52 insertions(+), 11 deletions(-)

Hi Paolo,

This patch appears to break qemu-system-sparc booting from CDROM with
the following command line:

./qemu-system-sparc -cdrom debian-40r4a-sparc-netinst.iso -boot d

Instead of booting straight into SILO, OpenBIOS hangs when trying to
read from the CDROM device.
   By using git bisect on master branch , I found this patch also break
qemu-system-arm from booting.
   command line:
  qemu-system-arm -M versatilepb -kernel vmlinuz-3.2.0-4-versatile
-initrd initrd.img-3.2.0-4-versatile -hda
/home/hitmoon/debian_wheezy_armel_standard.qcow2 -append 'root=/dev/sda1'

  The booting process stops at mounting the root partition and after
timeout droped into a initramfs shell. The device '/dev/sda1' is
presented . I guess it can not read properly from sda1.
I've just sent through a patch which fixes the issue for me - please
test and report back!

Paolo - not sure if it's worth a follow-up patch that renames the
relevant _readv/_writev functions in scsi-disk.c to _preadv/_pwritev to
try and help avoid such confusion in future?



  I can confirm it works for me !

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