From: Jim Fehlig <jfehlig@suse.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: ian.jackson@eu.citrix.com, wei.liu2@citrix.com, xen-devel@lists.xen.org
Subject: Re: [PATCH] libxl: don't add cache mode for empty drives
Date: Wed, 27 Apr 2016 10:22:10 -0600 [thread overview]
Message-ID: <5720E732.4030900@suse.com> (raw)
In-Reply-To: <20160427073847.wk3ieab5jobmni3a@mac>
On 04/27/2016 01:38 AM, Roger Pau Monné wrote:
> On Tue, Apr 26, 2016 at 10:35:31PM -0600, Jim Fehlig wrote:
>> qemu commit 91a097e7 forbids specifying the cache mode for empty
>> drives. Attempting to create a domain with an empty qdisk cdrom
>> results in
>>
>> qemu-system-x86_64: -drive if=ide,index=1,readonly=on,media=cdrom,
>> cache=writeback,id=ide-832: Must specify either driver or file
>>
>> Change libxl to only emit cache mode when a cdrom target is specified.
> What happens then when a cdrom is inserted? I cannot seem to find the code
> in libxl_cdrom_insert that sets the cache mode.
I cannot find it either. I suppose it would need to be setup via xenstore,
similar to other options like feature_discard. But looking at
$qemu-src/hw/block/xen_disk.c, it seems the XenBlkDev struct has no field to
specify cache mode. Would qemu's xen_disk need to be extended to support cache
mode, followed by a libxl patch to set the cache mode in xenstore?
> Is the default one used
> then?
Yes, the default cache mode (which is already writeback AIUI) would be used if
not explicitly specified. Which brings up the option of removing
'cache=writeback' for cdroms altogether. Any opinion on that option?
Regards,
Jim
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next prev parent reply other threads:[~2016-04-27 16:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-27 4:35 [PATCH] libxl: don't add cache mode for empty drives Jim Fehlig
2016-04-27 7:38 ` Roger Pau Monné
2016-04-27 16:22 ` Jim Fehlig [this message]
2016-04-28 8:27 ` George Dunlap
2016-04-28 9:17 ` Roger Pau Monné
2016-04-28 21:22 ` Jim Fehlig
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