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xen-devel
Re: [Xen-devel] [PATCH 3/7] xen/hvm: Xen PV extension of HVM initializa
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To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Subject: |
Re: [Xen-devel] [PATCH 3/7] xen/hvm: Xen PV extension of HVM initialization |
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From: |
Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> |
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Date: |
Wed, 3 Mar 2010 11:35:52 +0000 |
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Cc: |
Fitzhardinge <Jeremy.Fitzhardinge@xxxxxxxxxx>, Jeremy, Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>, "Yaozu \(Eddie\) Dong" <eddie.dong@xxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Stefano, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>, Sheng Yang <sheng@xxxxxxxxxxxxxxx> |
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Wed, 03 Mar 2010 03:32:28 -0800 |
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<1267436315-24486-1-git-send-email-sheng@xxxxxxxxxxxxxxx> <1267436315-24486-4-git-send-email-sheng@xxxxxxxxxxxxxxx> <4B8C63B0.2090507@xxxxxxxx> <201003020938.53630.sheng@xxxxxxxxxxxxxxx> <1267521735.11737.23107.camel@xxxxxxxxxxxxxxxxxxxxxx> <4B8D7248.5070807@xxxxxxxx> |
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Alpine 2.00 (DEB 1167 2008-08-23) |
On Tue, 2 Mar 2010, Jeremy Fitzhardinge wrote:
> On 03/02/2010 01:22 AM, Ian Campbell wrote:
> > On Tue, 2010-03-02 at 01:38 +0000, Sheng Yang wrote:
> >
> >> A annoy thing in pv drivers is that it would test if the domain type
> >> is _NOT_ XEN_NATIVE. So set the domain to XEN_HVM_DOMAIN would result
> >> in PV driver initialization then probably panic.
> >>
> > What _actually_ panics?
> >
> > Registration of the frontend devices should be completely harmless
> > (apart from a little wasted RAM) unless a xenbus driver manages to come
> > up and enumerate the xen bus and cause the ->probe function run.
> >
> > You should be gating the xenbus startup on the availability of PV
> > functionality not the individual driver registrations. This keeps the
> > test in a single easy to maintain place.
> >
> > Compare with pci_register_driver and all of the callers of that function
> > -- not a single one of them has an "is_pci_available" test anywhere.
> >
>
> The problem is that it currently assumes xenbus is initialized by the
> time the PV drivers init, because in a PV boot xenbus gets initted very
> early. We need to change it so that it can cope with drivers being
> initialized and registering with xenbus before it has been initialized.
>
> We have the same problem with plain PV-on-HVM drivers as xenbus only
> comes up as a result of probing the Xen PCI platform device, which may
> be after the PV drivers' init functions have been called.
Give a look at the fourth patch of the series I just posted: it
introduces a simple driver for the Xen PCI platform device to initialize
xenbus and gran table later on when running in a HVM domain, at the same
time leaving the PV case as it is.
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