Re: [Xen-devel] 2.6.37 PV on HVM issues

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Fri, 2010-12-03 at 16:29 +0000, Alex Bligh wrote:
> 
> --On 3 December 2010 11:24:43 +0000 Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
> wrote:
> 
> > On Fri, 2010-12-03 at 11:18 +0000, Stefano Stabellini wrote:
> >>
> >> If you know what you are doing you can manually remove the check for
> >> the unplug protocol in the kernel, just hack
> >> arch/x86/xen/platform-pci-unplug.c:check_platform_magic.
> >
> > This is exactly equivalent to adding "xen_emul_unplug=unnecessary" to
> > the kernel command line, isn't it?
> >
> > Conversely if you want to always force emulated devices (i.e. disable
> > any attempt to unplug) then "xen_emul_unplug=never" will do what you
> > want.
> 
> OK, I am confused. What I want do is is bring the PV devices up as
> /dev/xvda not /dev/sda. I don't much care whether or not it attempts to
> unplug the emulated devices, as I can cope with or without the additional
> presence of the emulated devices.
> 
> IE I want it to work just like it used to work with unmodified_drivers.
> 
> Is there a command line option for that?

Yes, it is "xen_emul_unplug=unnecessary" which tells the driver that you
know what you are doing and that it is not necessary to unplug the
emulated devices before enabling the pv path because you as the admin
have ensured that the pv path is safe to use.

Without this option present the default is to err on the side of caution
and not enable the pv path unless the emulated path can be unplugged.

Ian.

> Or if not, I am happy
> to try and work on a patch.



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