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Re: [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters for


From: Cong Meng
Subject: Re: [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive
Date: Thu, 23 Aug 2012 17:31:31 +0800
User-agent: Mozilla/5.0 (X11; Linux i686; rv:14.0) Gecko/20120714 Thunderbird/14.0



On Wed 22 Aug 2012 10:13:44 PM CST, Paolo Bonzini wrote:
Il 22/08/2012 15:13, Stefan Hajnoczi ha scritto:
http://lists.gnu.org/archive/html/qemu-devel/2010-12/msg01741.html

"This is a real problem in practice. IE. the USB CD-ROM on this POWER7
blade limits transfers to 0x1e000 bytes for example and the Linux "sr"
driver on the guest is going to try to give me bigger requests than that
if I don't start limiting them, which will cause all sort of errors."

It cannot be fixed for emulated SCSI HBAs in general but it can for
virtio-scsi.

For disks, this should be fixed simply by using scsi-block instead of
scsi-generic.

CD-ROMs are indeed more complicated because burning CDs cannot be done
with syscalls. :/


So, as the problem exist to CD-ROM, I will continue to get these patches move on.

As Paolo pointed out, the only limit is max_sectors (the total size of a scatter-list),
I will drop the other 2 parameters.

Paolo, what's your opinion?

Cong

Paolo





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