From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751217Ab2DTMwZ (ORCPT ); Fri, 20 Apr 2012 08:52:25 -0400 Received: from nat28.tlf.novell.com ([130.57.49.28]:43896 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750706Ab2DTMwY convert rfc822-to-8bit (ORCPT ); Fri, 20 Apr 2012 08:52:24 -0400 Message-Id: <4F917823020000780007EDDF@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.0 Date: Fri, 20 Apr 2012 13:52:19 +0100 From: "Jan Beulich" To: "Ian Campbell" , "Lin Ming" Cc: "Andrew Cooper" , "xen-devel@lists.xensource.com" , "Konrad Rzeszutek Wilk" , "linux-kernel@vger.kernel.org" Subject: Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall References: <1334913957.2863.1.camel@hp6530s> <4F913340.4000202@citrix.com> <1334920396.2863.16.camel@hp6530s> <1334925508.28331.63.camel@zakaz.uk.xensource.com> In-Reply-To: <1334925508.28331.63.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 20.04.12 at 14:38, Ian Campbell wrote: > On Fri, 2012-04-20 at 12:13 +0100, Lin Ming wrote: >> On Fri, 2012-04-20 at 10:58 +0100, Andrew Cooper wrote: >> > On 20/04/12 10:25, Lin Ming wrote: >> > > Implements xen_io_apic_read with hypercall, so it returns proper IO-APIC >> > > information instead of fabricated one. >> > > >> > > Signed-off-by: Lin Ming >> > > --- >> > > arch/x86/xen/apic.c | 16 +++++++++++----- >> > > 1 files changed, 11 insertions(+), 5 deletions(-) >> > > >> > > diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c >> > > index aee16ab..f1f392d 100644 >> > > --- a/arch/x86/xen/apic.c >> > > +++ b/arch/x86/xen/apic.c >> > > @@ -1,14 +1,20 @@ >> > > #include >> > > #include >> > > +#include >> > > +#include >> > > +#include >> > > >> > > unsigned int xen_io_apic_read(unsigned apic, unsigned reg) >> > > { >> > > - if (reg == 0x1) >> > > - return 0x00170020; >> > > - else if (reg == 0x0) >> > > - return apic << 24; >> > > + struct physdev_apic apic_op; >> > > + int ret; >> > > >> > > - return 0xff; >> > > + apic_op.apic_physbase = mpc_ioapic_addr(apic); >> > > + apic_op.reg = reg; >> > > + ret = HYPERVISOR_physdev_op(PHYSDEVOP_apic_read, &apic_op); >> > > + if (ret) >> > > + return ret; >> > > + return apic_op.value; >> > >> > Hypercall ret errors are negative, yet this function is unsigned. Given >> > that the previous function had no possible way to fail, perhaps on error >> > you should fake up the values as before. >> >> How about return -1 on error? >> The calling function can check -1 for error. > > Isn't -1 potentially (at least theoretically) a valid value to read from > one of these registers? > > Under what circumstances can these hypercalls fail? Only when the input is wrong (or it's not a privileged domain). > Would a BUG_ON be appropriate/ Probably. Jan