From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752166Ab2DTMic (ORCPT ); Fri, 20 Apr 2012 08:38:32 -0400 Received: from smtp.eu.citrix.com ([62.200.22.115]:40274 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751616Ab2DTMib (ORCPT ); Fri, 20 Apr 2012 08:38:31 -0400 X-IronPort-AV: E=Sophos;i="4.75,454,1330905600"; d="scan'208";a="12047897" Message-ID: <1334925508.28331.63.camel@zakaz.uk.xensource.com> Subject: Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall From: Ian Campbell To: Lin Ming CC: Andrew Cooper , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , "Konrad Rzeszutek Wilk" Date: Fri, 20 Apr 2012 13:38:28 +0100 In-Reply-To: <1334920396.2863.16.camel@hp6530s> References: <1334913957.2863.1.camel@hp6530s> <4F913340.4000202@citrix.com> <1334920396.2863.16.camel@hp6530s> Organization: Citrix Systems, Inc. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2-1 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Would a BUG_ON be appropriate/ > unsigned int ret = apic_read(...); > if (ret == -1) > //handle error. > > Thanks, > Lin Ming > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel