linux-kernel - Re: [Xen-devel] [PATCH v11 05/12] xen/pvh: Update E820 to work with PVH

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Date:	Thu, 19 Dec 2013 11:25:22 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Mukesh Rathor <mukesh.rathor@...cle.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
	<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>,
	<jbeulich@...e.com>
Subject: Re: [Xen-devel] [PATCH v11 05/12] xen/pvh: Update E820 to work with
 PVH

On Wed, 18 Dec 2013, Mukesh Rathor wrote:
> On Wed, 18 Dec 2013 18:25:15 +0000
> Stefano Stabellini <stefano.stabellini@...citrix.com> wrote:
> 
> > On Tue, 17 Dec 2013, Konrad Rzeszutek Wilk wrote:
> > > From: Mukesh Rathor <mukesh.rathor@...cle.com>
> > > 
> > > In xen_add_extra_mem() we can skip updating P2M as it's managed
> > > by Xen. PVH maps the entire IO space, but only RAM pages need
> > > to be repopulated.
> > > 
> > > Signed-off-by: Mukesh Rathor <mukesh.rathor@...cle.com>
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > > ---
> > >  arch/x86/xen/setup.c | 19 +++++++++++++++++--
> > >  1 file changed, 17 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> ........
> > > @@ -231,7 +246,7 @@ static void __init
> > > xen_set_identity_and_release_chunk( (void)HYPERVISOR_update_va_mapping(
> > >  			(unsigned long)__va(pfn << PAGE_SHIFT),
> > > pte, 0); }
> > > -
> > > +skip:
> > >  	if (start_pfn < nr_pages)
> > >  		*released += xen_release_chunk(
> > >  			start_pfn, min(end_pfn, nr_pages));
> ... 
> > Also considering that you are turning xen_release_chunk into a nop,
> > the only purpose of this function on PVH is to call
> > set_phys_range_identity. Can't we just do that?
> 
> xen_release_chunk() is called for PVH to give us the count of released,
> altho we don't need to release anything for pvh as it was already done in
> xen. The released count is then used later to add memory.
> 
> I had separate function to just adjust the stats, which is all we need
> to do for pvh, konrad just merged it with pv functions.

I see. I'll let Konrad decide which way is nicer.
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