netdev - Re: [Xen-devel] [PATCH v6] xen/grant-table: Avoid m2p

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Date:	Mon, 3 Feb 2014 11:13:35 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	Zoltan Kiss <zoltan.kiss@...rix.com>,
	Julien Grall <julien.grall@...aro.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	<jonathan.davies@...rix.com>, <wei.liu2@...rix.com>,
	<ian.campbell@...rix.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>
Subject: Re: [Xen-devel] [PATCH v6] xen/grant-table: Avoid m2p_override during
 mapping

On Mon, 3 Feb 2014, David Vrabel wrote:
> On 02/02/14 18:52, Zoltan Kiss wrote:
> > On 02/02/14 11:29, Julien Grall wrote:
> >> Hello,
> >>
> >> This patch is breaking Linux compilation on ARM:
> >>
> >> drivers/xen/grant-table.c: In function ‘__gnttab_map_refs’:
> >> drivers/xen/grant-table.c:989:3: error: implicit declaration of
> >> function ‘FOREIGN_FRAME’ [-Werror=implicit-function-declaration]
> >>     if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
> >>     ^
> >> drivers/xen/grant-table.c: In function ‘__gnttab_unmap_refs’:
> >> drivers/xen/grant-table.c:1054:3: error: implicit declaration of
> >> function ‘get_phys_to_machine’ [-Werror=implicit-function-declaration]
> >>     mfn = get_phys_to_machine(pfn);
> >>     ^
> >> drivers/xen/grant-table.c:1055:43: error: ‘FOREIGN_FRAME_BIT’
> >> undeclared (first use in this function)
> >>     if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
> >>                                             ^
> >> drivers/xen/grant-table.c:1055:43: note: each undeclared identifier is
> >> reported only once for each function it appears in
> >> drivers/xen/grant-table.c:1068:9: error: too many arguments to
> >> function ‘m2p_remove_override’
> >>           mfn);
> >>           ^
> >> In file included from include/xen/page.h:4:0,
> >>                   from drivers/xen/grant-table.c:48:
> >> /local/home/julien/works/midway/linux/arch/arm/include/asm/xen/page.h:106:19:
> >> note: declared here
> >>   static inline int m2p_remove_override(struct page *page, bool
> >> clear_pte)
> >>                     ^
> >> cc1: some warnings being treated as errors
> > 
> > Hi,
> > 
> > That's bad indeed. I think the best solution is to put those parts
> > behind an #ifdef x86. The ones moved from x86/p2m.c to grant-table.c.
> > David, Stefano, what do you think?
> 
> I don't think we want (more) #ifdef CONFIG_X86 in grant-table.c and the
> arch-specific bits will have to factored out into their own functions
> with suitable stubs provided for ARM.

We certainly don't want more ifdefs like that.


> But, this patch went in late and it's clearly not ready. So I think it
> should be reverted and we should aim to get it sorted out for 3.15.
> 
> Konrad/Stefano (if you agree) please revert
> 08ece5bb2312b4510b161a6ef6682f37f4eac8a1 and send a pull request.

Unfortunately I have to agree: fixing the prototype of
m2p_remove_override and replacing get_phys_to_machine with pfn_to_mfn is
easy.
However FOREIGN_FRAME is an x86-ism and I don't feel confortable with
adding yet another #define under arch/arm/xen just to deal with x86
stuff that spill on common code.

Sorry for not spotting this earlier.


> Konrad, I also think you should look at adding an ARM build to your test
> system (I thought you had this already).

Let's talk about how to set it up offline.