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[Xen-devel] Re: 2.6.37 PV on HVM and emul_unplug=unnecessary

To: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Subject: [Xen-devel] Re: 2.6.37 PV on HVM and emul_unplug=unnecessary
From: Alex Bligh <alex@xxxxxxxxxxx>
Date: Wed, 12 Jan 2011 13:25:15 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Alex Bligh <alex@xxxxxxxxxxx>
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--On 12 January 2011 14:04:57 +0100 Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:

Something similar was done in the 2.6.18 "XenoLinux" kernels, but it's
ugly and it touches into areas of the kernell that Xen support shouldn't

If your "Xen Dom0 prior to 3.4.something" is RHEL/CentOS, the 5.6 version
will include a backport of PCI unplug support.  Then you only need to bug
your cloud provider. :)

I am the cloud provider. The real fix is to move to Xen 4.0.1. Part of
the issue, however, is moving to 4.0.1 will make a subset of guests
behave differently from others, as suddenly their /dev/sda will disappear.
We know there are people who don't use standard installs so possibly
unknowingly are not using pv drivers (e.g. they have /dev/sdaX in their
fstab). It would be nice if I could separate this change from the rest
of the 4.0.1 upgrade, as this would make a 4.0.1 upgrade less scary.
It would be oh-so-much-easier-for-me if /dev/sdaX disappeared when
they upgraded their kernel, rather than when I make a later change.

However, if could point me at a working changeset which contains the
backport, that would be really useful. Stefano posted one which I
think he marked as "untested".

Alex Bligh

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