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Date: Thu, 29 Mar 2012 15:21:48 +0100
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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To: "Wei Liu (Intern)" <wei.liu2@citrix.com>
CC: Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
        Konrad Rzeszutek Wilk <konrad@darnok.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
        "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [Xen-devel] [PATCH] xen-blkfront: set pages are FOREIGN_FRAME
 when sharing them
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On Thu, 29 Mar 2012, Wei Liu (Intern) wrote:
> On Thu, 2012-03-29 at 14:56 +0100, Stefano Stabellini wrote:
> > On Tue, 27 Mar 2012, Konrad Rzeszutek Wilk wrote:
> > > On Tue, Mar 27, 2012 at 02:49:58PM +0100, Stefano Stabellini wrote:
> > > > Set pages as FOREIGN_FRAME whenever blkfront shares them with another
> > > > domain. Then when blkfront un-share them, also removes the
> > > > FOREIGN_FRAME_BIT from the p2m.
> > > > 
> > > > We do it so that when the source and the destination domain are the same
> > > > (blkfront connected to blkback in the same domain) we can more easily
> > > > recognize which ones are the source pfns and which ones are the
> > > > destination pfns (both are going to be pointing to the same mfns).
> > > > 
> > > > Without this patch enstablishing a connection between blkfront and QEMU
> > > > qdisk in the same domain causes QEMU to hang and never return.
> > > > Considering that it fixes a serious bug, it should be backported to
> > > > previous releases.
> > > 
> > > 
> > > ERROR: "set_phys_to_machine" [drivers/block/xen-blkfront.ko] undefined!
> > 
> > I cannot reproduce this error: set_phys_to_machine is defined in
> > arch/x86/include/asm/xen/page.h, that is included by include/xen/page.h,
> > that is included by blkfront).
> > What CS did you apply this patch to? What is your config?
> > 
> 
> In arch/x86/xen/p2m.c, set_phys_to_machine is not exported. You need
> another patch to do that.
> 
> It might be that you were using a monolithic kernel so that you didn't
> see this error.

Yes, you are right. Thanks!
I'll write another patch to export set_phys_to_machine.