From: Lin Ming Subject: Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall Date: Fri, 20 Apr 2012 19:13:16 +0800 Message-ID: <1334920396.2863.16.camel@hp6530s> References: <1334913957.2863.1.camel@hp6530s> <4F913340.4000202@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F913340.4000202@citrix.com> Sender: linux-kernel-owner@vger.kernel.org To: Andrew Cooper Cc: Konrad Rzeszutek Wilk , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" List-Id: xen-devel@lists.xenproject.org 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. unsigned int ret = apic_read(...); if (ret == -1) //handle error. Thanks, Lin Ming