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

From: Mark Cave-Ayland
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH 4/7] scsi-disk: introduce dma_readv and dma_writev
Date: Fri, 3 Jun 2016 06:22:42 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.8.0

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
>>> allow
>>> >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.
> Paolo:
>   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?



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