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Re: [Xen-devel] feature flags use

from [Jan Beulich]

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To:	<xen-devel@xxxxxxxxxxxxxxxxxxx>,"Keir Fraser" <keir@xxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] feature flags use
From:	"Jan Beulich" <jbeulich@xxxxxxxxxx>
Date:	Fri, 10 Nov 2006 15:59:27 +0100
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>That flag is treated oddly. Actually we detect if the kernel uses Elf notes
>or whether it has the string PAE=yes[extended]. In either case we notify the
>hypervisor via *vm_assist*! This then decides whether or not we advertise
>the XENFEAT flag to the domU.

I was talking about XENFEAT_pae_pgdir_above_4gb - this flag appears to be
be useless.
Also, regardless of whether you advertise support for the feature to a domU,
the code inside Xen doesn't treat the two cases (kernel with and without this
flag set) differently.

>Anyway, what feature flag do you want to add? Is this to distinguish PV PAE
>guest from PV 64-bit guest?

At this point I was thinking about that hypervisor_virt_start change that the
kernel needs to advertise it can deal with.

Jan



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