linux-kernel - Re: [PATCH v2 4/8] xen: Use the correctly the Xen memory terminologies

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Message-ID: <20150805165225.GC3603@dtor-ws>
Date:	Wed, 5 Aug 2015 09:52:25 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	Julien Grall <julien.grall@...rix.com>,
	xen-devel@...ts.xenproject.org, ian.campbell@...rix.com,
	linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Roger Pau Monné <roger.pau@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>, Juergen Gross <jgross@...e.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-input@...r.kernel.org, netdev@...r.kernel.org,
	linux-scsi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-fbdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 4/8] xen: Use the correctly the Xen memory
 terminologies

On Wed, Aug 05, 2015 at 11:08:55AM +0100, Stefano Stabellini wrote:
> On Tue, 4 Aug 2015, Julien Grall wrote:
> > Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
> > is meant, I suspect this is because the first support for Xen was for
> > PV. This resulted in some misimplementation of helpers on ARM and
> > confused developers about the expected behavior.
> > 
> > For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
> > Although, if we look at the implementation on x86, it's returning a GFN.
> > 
> > For clarity and avoid new confusion, replace any reference to mfn with
> > gfn in any helpers used by PV drivers. The x86 code will still keep some
> > reference of pfn_to_mfn but exclusively for PV (a BUG_ON has been added
> > to ensure this). No changes as been made in the hypercall field, even
> > though they may be invalid, in order to keep the same as the defintion
> > in xen repo.
> > 
> > Take also the opportunity to simplify simple construction such
> > as pfn_to_mfn(page_to_pfn(page)) into page_to_gfn. More complex clean up
> > will come in follow-up patches.
> > 
> > [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb
> > 
> > Signed-off-by: Julien Grall <julien.grall@...rix.com>
> > Cc: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > Cc: Russell King <linux@....linux.org.uk>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> > Cc: David Vrabel <david.vrabel@...rix.com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: x86@...nel.org
> > Cc: "Roger Pau Monné" <roger.pau@...rix.com>
> > Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > Cc: Ian Campbell <ian.campbell@...rix.com>
> > Cc: Wei Liu <wei.liu2@...rix.com>
> > Cc: Juergen Gross <jgross@...e.com>
> > Cc: "James E.J. Bottomley" <JBottomley@...n.com>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Jiri Slaby <jslaby@...e.com>
> > Cc: Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
> > Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> > Cc: linux-input@...r.kernel.org
> > Cc: netdev@...r.kernel.org
> > Cc: linux-scsi@...r.kernel.org
> > Cc: linuxppc-dev@...ts.ozlabs.org
> > Cc: linux-fbdev@...r.kernel.org
> > Cc: linux-arm-kernel@...ts.infradead.org
> 
> Aside from the x86 bits:
> 
> Reviewed-by: Stefano Stabellini <stefano.stabellini@...citrix.com>

Not really important, but just in case anyone waits for my ack on input
bits:

Acked-by: Dmitry Torokhov <dmitry.torokhov@...il.com>

Thanks.

-- 
Dmitry
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