linux-kernel - Re: [Xen-devel] [PATCH v4] xen PVonHVM: move shared

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Message-Id: <5090E93302000078000A59C8@nat28.tlf.novell.com>
Date:	Wed, 31 Oct 2012 08:02:43 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Olaf Hering" <olaf@...fle.de>
Cc:	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"xen-devel" <xen-devel@...ts.xen.org>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH v4] xen PVonHVM: move shared_info to
 reserved memory area

>>> On 30.10.12 at 18:03, Olaf Hering <olaf@...fle.de> wrote:
> On Tue, Oct 30, Jan Beulich wrote:
> 
>> And iirc you're doing this relocation because otherwise the newly
>> booting kernel image may get overwritten at an (from its
>> perspective) arbitrary location. What I'm trying to point out is
>> that the shared info structure is not the only thing (potentially)
>> inside the kernel image that might get overwritten - the relocated
>> (by the old kernel) vCPU info may as well. Plus I think the new
>> kernel has no way of relocating it a second time (including back
>> into the shared info structure) with how the hypervisor works at
>> present.
> 
> Thanks, I have not looked at this, nor was I aware of it until now.
> I will see what needs to be done.
> 
> Is this also an issue with the xenlinux based PVonHVM code?

No - this code doesn't make use of that feature (yet, we've got
a feature request that would involve doing so), as it only ever
touches vCPU 0's info.

Jan

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