Subject: Re: kvm PCI assignment & VFIO ramblings

From: "Roedel, Joerg" <[email-masked]>
Date: Wed, 24 Aug 2011 10:53:21 +0200

On Tue, Aug 23, 2011 at 07:35:37PM -0400, Benjamin Herrenschmidt wrote:
> On Tue, 2011-08-23 at 15:18 +0200, Roedel, Joerg wrote:

> > Hmm, good idea. But as far as I know the hotplug-event needs to be in
> > the guest _before_ the device is actually unplugged (so that the guest
> > can unbind its driver first). That somehow brings back the sleep-idea
> > and the timeout in the .release function.
> 
> That's for normal assisted hotplug, but don't we support hard hotplug ?
> I mean, things like cardbus, thunderbolt (if we ever support that)
> etc... will need it and some platforms do support hard hotplug of PCIe
> devices.
> 
> (That's why drivers should never spin on MMIO waiting for a 1 bit to
> clear without a timeout :-)

Right, thats probably the best semantic for this issue then. The worst
thing that happens is that the admin crashed the guest.

	Joerg

-- 
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632