linux-kernel - RE: [PATCH 2/2] xen/x86: Implement x86_apic

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Message-ID: <B6C2EB9186482D47BD0C5A9A483456440E05E7@SHSMSX101.ccr.corp.intel.com>
Date:	Tue, 17 Apr 2012 00:52:06 +0000
From:	"Zhang, Xiantao" <xiantao.zhang@...el.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Lin Ming <mlin@...pku.edu.cn>
CC:	"mingo@...e.hu" <mingo@...e.hu>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"jwboyer@...hat.com" <jwboyer@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Zhang, Xiantao" <xiantao.zhang@...el.com>
Subject: RE: [PATCH 2/2] xen/x86: Implement x86_apic_ops



> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@...cle.com]
> Sent: Monday, April 16, 2012 11:48 PM
> To: Lin Ming
> Cc: mingo@...e.hu; Siddha, Suresh B; jwboyer@...hat.com; hpa@...or.com;
> yinghai@...nel.org; linux-kernel@...r.kernel.org; Zhang, Xiantao
> Subject: Re: [PATCH 2/2] xen/x86: Implement x86_apic_ops
> 
> On Wed, Apr 11, 2012 at 12:49:02PM +0800, Lin Ming wrote:
> > On Thu, Mar 29, 2012 at 1:37 AM, Konrad Rzeszutek Wilk
> > <konrad.wilk@...cle.com> wrote:
> > > Or rather just implement one different function as opposed to the
> > > native one : the read function.
> > >
> > > We synthesize the values.
> > >
> > > Acked-by:  Suresh Siddha <suresh.b.siddha@...el.com>
> > > [v1: Rebased on top of tip/x86/urgent]
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > > ---
> > >  arch/x86/xen/Makefile    |    2 +-
> > >  arch/x86/xen/apic.c      |   17 +++++++++++++++++
> > >  arch/x86/xen/enlighten.c |    2 ++
> > >  arch/x86/xen/xen-ops.h   |    4 ++++
> > >  4 files changed, 24 insertions(+), 1 deletions(-)
> > >  create mode 100644 arch/x86/xen/apic.c
> > >
> > > diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile index
> > > add2c2d..96ab2c0 100644
> > > --- a/arch/x86/xen/Makefile
> > > +++ b/arch/x86/xen/Makefile
> > > @@ -20,5 +20,5 @@ obj-$(CONFIG_EVENT_TRACING) += trace.o
> > >  obj-$(CONFIG_SMP)              += smp.o
> > >  obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o
> > >  obj-$(CONFIG_XEN_DEBUG_FS)     += debugfs.o
> > > -obj-$(CONFIG_XEN_DOM0)         += vga.o
> > > +obj-$(CONFIG_XEN_DOM0)         += apic.o vga.o
> > >  obj-$(CONFIG_SWIOTLB_XEN)      += pci-swiotlb-xen.o diff --git
> > > a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c new file mode 100644
> > > index 0000000..aee16ab
> > > --- /dev/null
> > > +++ b/arch/x86/xen/apic.c
> > > @@ -0,0 +1,17 @@
> > > +#include <linux/init.h>
> > > +#include <asm/x86_init.h>
> > > +
> > > +unsigned int xen_io_apic_read(unsigned apic, unsigned reg) {
> > > +       if (reg == 0x1)
> > > +               return 0x00170020;
> > > +       else if (reg == 0x0)
> > > +               return apic << 24;
> >
> > Why is fixed value returned?
> >
> > Can't we implement it with hypercall(PHYSDEVOP_apic_read)?
> 
> We sure can. But this was meant to fix the regression - so I figured we would
> do that later on. But the more important question is - do we actually need to
> do the hypercall? We aren't using the IOAPIC for anything - we don't program
> the pins from dom0.

 Actually, dom0 doesn't programe ioapic pins directly as you said,  but the work is done by dom0 in the indirect way.  For dom0,  I added a hypercall PHYSDEVOP_setup_gsi before, and with this hypercall, we can get rid of programing IOAPIC pins from dom0 and hypervisor helps to do the ioapic programming, but we still need to get correct GSI information from hypervisor, otherwise, the hypercall may meet issues.  
Xiantao 


> >
> > Lin Ming
> >
> > > +
> > > +       return 0xff;
> > > +}
> > > +
> > > +void __init xen_init_apic(void)
> > > +{
> > > +       x86_io_apic_ops.read = xen_io_apic_read; }
> > > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> > > index 4172af8..a7df080 100644
> > > --- a/arch/x86/xen/enlighten.c
> > > +++ b/arch/x86/xen/enlighten.c
> > > @@ -1271,6 +1271,8 @@ asmlinkage void __init xen_start_kernel(void)
> > >                xen_start_info->console.domU.mfn = 0;
> > >                xen_start_info->console.domU.evtchn = 0;
> > >
> > > +               xen_init_apic();
> > > +
> > >                /* Make sure ACS will be enabled */
> > >                pci_request_acs();
> > >        }
> > > diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index
> > > b095739..45c0c06 100644
> > > --- a/arch/x86/xen/xen-ops.h
> > > +++ b/arch/x86/xen/xen-ops.h
> > > @@ -92,11 +92,15 @@ struct dom0_vga_console_info;
> > >
> > >  #ifdef CONFIG_XEN_DOM0
> > >  void __init xen_init_vga(const struct dom0_vga_console_info *,
> > > size_t size);
> > > +void __init xen_init_apic(void);
> > >  #else
> > >  static inline void __init xen_init_vga(const struct
> > > dom0_vga_console_info *info,
> > >                                       size_t size)
> > >  {
> > >  }
> > > +static inline void __init xen_init_apic(void) { }
> > >  #endif
> > >
> > >  /* Declare an asm function, along with symbols needed to make it
> > > --
> > > 1.7.7.5
> > --
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