linux-kernel - Re: [Xen-devel] [PATCH 06/11] xen/mmu: For 64-bit do not call xen_map_identity

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Date:	Mon, 20 Aug 2012 12:45:45 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Jan Beulich <JBeulich@...ell.com>
Subject: Re: [Xen-devel] [PATCH 06/11] xen/mmu: For 64-bit do not call
 xen_map_identity_early

On Fri, 17 Aug 2012, Konrad Rzeszutek Wilk wrote:
> On Fri, Aug 17, 2012 at 06:41:23PM +0100, Stefano Stabellini wrote:
> > On Thu, 16 Aug 2012, Konrad Rzeszutek Wilk wrote:
> > > B/c we do not need it. During the startup the Xen provides
> > > us with all the memory mapped that we need to function.
> > 
> > Shouldn't we check to make sure that is actually true (I am thinking at
> > nr_pt_frames)?
> 
> I was looking at the source code (hypervisor) to figure it out and
> that is certainly true.
> 
> 
> > Or is it actually stated somewhere in the Xen headers?
> 
> Couldn't find it, but after looking so long at the source code
> I didn't even bother looking for it.
> 
> Thought to be honest - I only looked at how the 64-bit pagetables
> were set up, so I didn't dare to touch the 32-bit. Hence the #ifdef

I think that we need to involve some Xen maintainers and get this
written down somewhere in the public headers, otherwise we have no
guarantees that it is going to stay as it is in the next Xen versions.

Maybe we just need to add a couple of lines of comment to
xen/include/public/xen.h.
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