WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] [PATCH, RFC]: qemu: hang-free/error-tolerant PCI hot-plu

To: Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH, RFC]: qemu: hang-free/error-tolerant PCI hot-plug protocol
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Fri, 30 Jul 2010 14:40:13 +0100
Cc: Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Fri, 30 Jul 2010 06:41:11 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <1280426058.1723.2266.camel@xxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Newsgroups: chiark.mail.xen.devel
References: <1280426058.1723.2266.camel@xxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Gianni Tedesco writes ("[Xen-devel] [PATCH, RFC]: qemu: 
hang-free/error-tolerant PCI hot-plug protocol"):
> The interface for PCI hotplug is flexible enough to shoot ones-self in
> the foot. It is possible to try to insert a PCI device in to a slot
> already occupied by a qemu emulated device (NIC, PIIX, ISA-bridge, etc.)
> In this case qemu (wisely) refuses to do the hotplug. Since there is no
> way for a toolstack to query qemu's pci device layout there is no way to
> check for this ahead of time. In this case the toolstack must wait for
> device-model state to change to pci-inserted which never happens.

Hrm.

> I propose that when qemu decides not to hot-plug a device that it raise
> the "pci-inserted" status anyway. The tools must then check the
> "parameter" key in xenbus for a non-error string. In other words:

Why do this rather than a new status "pci-insert-failed" ?  How does
this affect existing toolstacks ?

> --- a/hw/piix4acpi.c
> +++ b/hw/piix4acpi.c

I haven't looked at the code near here.  Does qemu log anything ?  If
so then the corresponding toolstack patches should say "consult qemu
logfile".  Otherwise perhaps qemu should.

Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel