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Re: [for-4.2 PATCH 3/6] replay: update docs for record/replay with block
From: |
Kevin Wolf |
Subject: |
Re: [for-4.2 PATCH 3/6] replay: update docs for record/replay with block devices |
Date: |
Fri, 11 Oct 2019 11:12:32 +0200 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
Am 11.10.2019 um 08:10 hat Pavel Dovgalyuk geschrieben:
> > From: Kevin Wolf [mailto:address@hidden]
> > Am 25.09.2019 um 11:02 hat Pavel Dovgalyuk geschrieben:
> > > I started playing with -blockdev: added new blockdev for blkreplay and
> > > constructed the following command line:
> > >
> > > -blockdev driver=file,filename=disk.img,node-name=hd0
> > > -blockdev driver=blkreplay,file=hd0,node-name=hd0-rr
> > > -device virtio-blk-device,drive=hd0-rr
> > >
> > > However, I get an error: "Could not open 'disk.img': Permission denied"
> > > Everything works when I use this file in '-drive' parameter.
> > > What am I doing wrong?
> >
> > The reason why I didn't reply immediately is because I don't see
> > anything wrong in the options you used.
> >
> > Just to confirm, do you still get the same error when you use only the
> > first -blockdev option and no other options at all?
>
> Ok, I tried again and got different error, which was caused by incorrect
> QAPI schema for blkreplay.
> Now it seems ok, but I still can't boot.
Hm... Are you actually using a raw image? If not, you need the format
driver, too, and would end up with something like:
-blockdev driver=file,filename=disk.qcow2,node-name=hd0
-blockdev driver=qcow2,file=hd0,node-name=hd0-qcow2
-blockdev driver=blkreplay,file=hd0-qcow2,node-name=hd0-rr
-device virtio-blk-device,drive=hd0-rr
(The first two can be combined into a single option by using a syntax
like file.driver=file,file.filename=disk.qcow2, but defining each node
separately is a bit cleaner.)
> > I've now tried out the options you gave, and it does fail for me, but
> > with a different error:
> >
> > qemu-system-x86_64: -blockdev
> > driver=blkreplay,file=hd0,node-name=hd0-rr: Invalid
> > parameter 'blkreplay'
> >
> > This one is because the QAPI schema doesn't know blkreplay and should
> > easily be fixed by adding a blkreplay field to BlockdevOptions.
>
> Right, I added the following schema:
>
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2832,8 +2832,8 @@
> # Since: 2.9
> ##
> { 'enum': 'BlockdevDriver',
> - 'data': [ 'blkdebug', 'blklogwrites', 'blkverify', 'bochs', 'cloop',
> - 'copy-on-read', 'dmg', 'file', 'ftp', 'ftps', 'gluster',
> + 'data': [ 'blkdebug', 'blklogwrites', 'blkreplay', 'blkverify', 'bochs',
> + 'cloop', 'copy-on-read', 'dmg', 'file', 'ftp', 'ftps', 'gluster',
> 'host_cdrom', 'host_device', 'http', 'https', 'iscsi', 'luks',
> 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels', 'qcow',
> 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
Please add a '@blkreplay: Since 4.2' note to the comment, too.
> @@ -3446,6 +3446,18 @@
> 'data': { 'test': 'BlockdevRef',
> 'raw': 'BlockdevRef' } }
>
> +##
> +# @BlockdevOptionsBlkreplay:
> +#
> +# Driver specific block device options for blkreplay.
> +#
> +# @image: disk image which should be controlled with blkreplay
> +#
> +# Since: 4.2
> +##
> +{ 'struct': 'BlockdevOptionsBlkreplay',
> + 'data': { 'image': 'BlockdevRef' } }
> +
> ##
> # @QuorumReadPattern:
> #
> @@ -3973,6 +3985,7 @@
> 'blkdebug': 'BlockdevOptionsBlkdebug',
> 'blklogwrites':'BlockdevOptionsBlklogwrites',
> 'blkverify': 'BlockdevOptionsBlkverify',
> + 'blkreplay': 'BlockdevOptionsBlkreplay',
> 'bochs': 'BlockdevOptionsGenericFormat',
> 'cloop': 'BlockdevOptionsGenericFormat',
> 'copy-on-read':'BlockdevOptionsGenericFormat',
Otherwise, this looks good to me. Can you turn it into a proper patch?
> > As soft freeze is coming closer, I'm considering taking this series as
> > it is (it's wrong in parts, but the old state is probably even more
> > wrong) and letting you fix up these checks on top. What do you think?
>
> That sounds reasonable.
Okay, then that's what I will do.
Kevin