linux-kernel - Re: [PATCH 2/4] x86,xen: introduce x86_init.mapping.pagetable

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Date:	Mon, 18 Apr 2011 15:09:21 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"jeremy@...p.org" <jeremy@...p.org>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [PATCH 2/4] x86,xen: introduce
 x86_init.mapping.pagetable_reserve

On Thu, 14 Apr 2011, Stefano Stabellini wrote:
> On Thu, 14 Apr 2011, H. Peter Anvin wrote:
> > On 04/14/2011 04:30 AM, Stefano Stabellini wrote:
> > > 
> > > I hope that the other email I have just sent clarifies the purpose of
> > > the hook.
> > > 		
> > 
> > You're commingling rationale and (proposed) semantics.  BOTH need to be
> > stated clearly.
> 
> Sorry I didn't answer the right question straight away.
> The semantics follow:
> 
> 
> 
> It is as if there is an implicit pvop after find_early_table_space
> that exports the range pgt_buf_start - pgt_buf_top.
> The range indicated is used, and it is the only range used, for the initial
> kernel pagetable pages.
> The range indicated is an overestimate.
> It is implicit because we use the pgt_buf_* variables directly but
> nonetheless it was in the first version of the patch.
> 
> After the pagetable setup done by kernel_physical_mapping_init, we know
> exactly how many pages we actually used for the initial kernel
> pagetables and how many are left unused.
> 
> The purpose of the second pvop (x86_init.mapping.pagetable_reserve) is
> to notify sub-architectures of the actual range used for initial kernel
> pagetable pages and partially revoke the previous indication.
> 
> 
> 
> If you agree with the proposed semantics above, I'll add the description
> to the commit message as well as the code. I could also modify the
> syntax of the new pvop call to better suit the semantics and/or restore
> the first pvop call.
> 

ping?


Sorry, I don't mean to be pushy, it is just that I'll be AFK for 12 days
starting from next Friday and I think that this issue should really be
fixed in time for the 2.6.39 release, otherwise no 2.6.39 kernels will
be able to boot on any xen system.
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