On 23.02.2016 18:16, Kevin Wolf wrote: > This patch adds an option to the drive_add HMP command to create only a > BlockDriverState without a BlockBackend on top. > > The motivation for this is that libvirt needs to specify options to a > migration target (specifically, detect-zeroes). drive-mirror doesn't > allow specifying options, and the proper way to do this is to create the > target BDS separately with blockdev-add (where you can specify options) > and then use blockdev-mirror to that BDS. > > However, libvirt can't use blockdev-add as long as it is still > experimental, and we're expecting that it will still take some time, so > we need to resort to drive_add. > > The problem with drive_add is that so far it always created a BB, and > BDSes with a BB can't be used as a mirroring target as long as we don't > support multiple BBs per BDS - and while we're working towards that > goal, it's another thing that will still take some time. > > So to achieve the goal, the simplest solution to provide the > functionality now without adding one-off options to the mirror QMP > commands is to extend drive_add to create nodes without BBs. > > Signed-off-by: Kevin Wolf <[email protected]> > --- > blockdev.c | 30 ++++++++++++++++++++++++++++++ > device-hotplug.c | 7 +++++++ > hmp-commands.hx | 4 ++-- > include/block/block_int.h | 2 ++ > 4 files changed, 41 insertions(+), 2 deletions(-) >
Patch looks good to me (well, except for it being a pity we have to fall
back on this HMP command), I only have a minor suggestion:
[...]
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index bb52e4d..3b44e52 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1200,8 +1200,8 @@ ETEXI
>
> {
> .name = "drive_add",
> - .args_type = "pci_addr:s,opts:s",
> - .params = "[[<domain>:]<bus>:]<slot>\n"
> + .args_type = "node:-n,pci_addr:s,opts:s",
> + .params = "[-n] [[<domain>:]<bus>:]<slot>\n"
> "[file=file][,if=type][,bus=n]\n"
> "[,unit=m][,media=d][,index=i]\n"
> "[,cyls=c,heads=h,secs=s[,trans=t]]\n"
The description reads:
> Add drive to PCI storage controller.
Maybe this should be extended now?
Max
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