From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH] xen/apic: implement io apic read with
 hypercall
Date: Thu, 26 Apr 2012 11:33:46 -0400
Message-ID: <20120426153346.GC26830@phenom.dumpdata.com>
References: <1334913957.2863.1.camel@hp6530s> <4F913340.4000202@citrix.com>
	<1334920396.2863.16.camel@hp6530s>
	<1334925508.28331.63.camel@zakaz.uk.xensource.com>
	<20120420164150.GC31062@phenom.dumpdata.com>
	<CAF1ivSamaYzQDwjFqRGrnQ+fCr0D4vLGuG4JRBZ3_GD_y8yY=A@mail.gmail.com>
	<20120423151123.GC24481@phenom.dumpdata.com>
	<CAF1ivSY1GAkqU2gN0P22Tb0pmwagam5UUVMABSgnoH3+C+TY+A@mail.gmail.com>
	<20120424162321.GH3213@phenom.dumpdata.com>
	<CAF1ivSYFp7duSCNb+_5teM83icx1O-rY0YVFm7Laq_JLZuzerw@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Return-path: <xen-devel-bounces@lists.xen.org>
Content-Disposition: inline
In-Reply-To: <CAF1ivSYFp7duSCNb+_5teM83icx1O-rY0YVFm7Laq_JLZuzerw@mail.gmail.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Lin Ming <mlin@ss.pku.edu.cn>
Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Ian Campbell <Ian.Campbell@citrix.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
List-Id: xen-devel@lists.xenproject.org

> >>
> >> unsigned int xen_io_apic_read(unsigned apic, unsigned reg)
> >> {
> >> =A0 =A0 =A0 =A0 struct physdev_apic apic_op;
> >> =A0 =A0 =A0 =A0 int ret;
> >>
> >> =A0 =A0 =A0 =A0 apic_op.apic_physbase =3D mpc_ioapic_addr(apic);
> >> =A0 =A0 =A0 =A0 apic_op.reg =3D reg;
> >> =A0 =A0 =A0 =A0 ret =3D HYPERVISOR_physdev_op(PHYSDEVOP_apic_read, &ap=
ic_op);
> >> =A0 =A0 =A0 =A0 if (!ret)
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return apic_op.value;
> >>
> >> =A0 =A0 =A0 =A0 /* emulate register */
> >> =A0 =A0 =A0 =A0 if (reg =3D=3D 0x1)
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return 0x00170020;
> >> =A0 =A0 =A0 =A0 else if (reg =3D=3D 0x0)
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return apic << 24;
> >> =A0 =A0 =A0 =A0 else
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return -1;
> >
> > =A0 =A0 =A0 =A0return 0xfd;
> =

> Where does this magic number 0xfd come from?
> =

> Both native_io_apic_read and xen_io_apic_read does not return 0xfd on err=
or.

That is correct. But that is what it should have been. Suresh
pointed that out sometime and I managed to lose that part in one of the
commits. The earlier patch of this version did that.

Thought thinking about it this some I am not sure if 0xff is a better
choice... In the end it probably does not matter the slighest.