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Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from devic
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal |
Date: |
Mon, 8 Nov 2010 23:02:50 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Nov 05, 2010 at 05:01:49PM +0100, Markus Armbruster wrote:
> "Michael S. Tsirkin" <address@hidden> writes:
>
> > On Fri, Nov 05, 2010 at 02:27:49PM +0100, Markus Armbruster wrote:
> >> I'd be fine with any of these:
> >>
> >> 1. A new command "device_disconnet ID" (or similar name) to disconnect
> >> device ID from any host parts. Nice touch: you don't have to know
> >> about the device's host part(s) to disconnect it. But it might be
> >> more work than the other two.
> >>
> >> 2. New commands netdev_disconnect, drive_disconnect (or similar names)
> >> to disconnect a host part from a guest device. Like (1), except you
> >> have to point to the other end of the connection to cut it.
> >
> > I think it's cleaner not to introduce a concept of a disconnected
> > backend.
>
> Backends start disconnected, so the concept already exists.
>
> > One thing that we must be careful to explicitly disallow, is
> > reconnecting guest to another host backend. The reason being
> > that guest might rely on backend features and changing these
> > would break this.
> >
> > Given that, disconnecting without delete isn't helpful.
>
> What about disconnect, hot plug new device, connect?
Exactly. I don't think we want to support this.
New device might not support all features that old one has.
Or it may have more features.
> >> 3. A new command "drive_del ID" similar to existing netdev_del. This is
> >> (2) fused with delete. Conceptual wart: you can't disconnect and
> >> keep the host part around. Moreover, delete is slightly dangerous,
> >> because it renders any guest device still using the host part
> >> useless.
> >
> > I don't see how it's more dangerous than disconnecting.
> > If guest can't access the backend it might not exist
> > as far as guest is concerned.
>
> If we keep disconnect and delete separate operations, we can make delete
> fail when still connected. Typo insurance.
>
> >> Do you need anything else from me to make progress?
> >
> > Let's go for 3. Need for 1/2 seems dubious, and it's much harder
> > to support.
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, (continued)
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, Ryan Harper, 2010/11/08
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, Daniel P. Berrange, 2010/11/08
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, Michael S. Tsirkin, 2010/11/08
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, Michael S. Tsirkin, 2010/11/05
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, Ryan Harper, 2010/11/05
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal, Markus Armbruster, 2010/11/05
- Re: [Qemu-devel] [PATCH 0/3] v4 Decouple block device removal from device removal,
Michael S. Tsirkin <=