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Date: Fri, 11 May 2012 21:20:08 -0400
From: "Shai Fultheim (Shai@...leMP.com)" <Shai@...leMP.com>
To: Ido Yariv <ido@...ery.com>, "H. Peter Anvin" <hpa@...or.com>
CC: Ingo Molnar <mingo@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: RE: [PATCH v4] vsmp: Fix number of CPUs when vsmp is disabled
Looks good.
--Shai
> -----Original Message-----
> From: Ido Yariv [mailto:ido@...ery.com]
> Sent: Friday, May 11, 2012 12:27
> To: H. Peter Anvin
> Cc: Ingo Molnar; linux-kernel@...r.kernel.org; Ingo Molnar; Thomas
> Gleixner; Shai Fultheim (Shai@...leMP.com)
> Subject: Re: [PATCH v4] vsmp: Fix number of CPUs when vsmp is disabled
>
> Hi,
>
> On Wed, May 09, 2012 at 08:55:54AM -0700, H. Peter Anvin wrote:
> > On 05/09/2012 08:44 AM, Ingo Molnar wrote:
> > >
> > > * Ido Yariv <ido@...ery.com> wrote:
> > >
> > >> +static void __init vsmp_cap_cpus(void)
> > >> +{
> > >> + void __iomem *address;
> > >> + unsigned int cfg, topology, node_shift, maxcpus;
> > >> +
> > >> +#ifdef CONFIG_X86_VSMP
> > >> + /* VSMP is enabled, no need to cap cpus */
> > >> + return;
> > >> +#elif defined(CONFIG_SMP)
> > >> + /*
> > >> + * CONFIG_X86_VSMP is not configured, so limit the number CPUs to
> the
> > >
> > > I suspect this will throw compiler warnings in the
> > > CONFIG_X86_VSMP && !CONFIG_SMP case.
> > >
> >
> > What on Earth is the point of allowing that combination? Why not make
> > X86_VSMP depend on SMP and reduce the testing matrix?
>
> CONFIG_X86_VSMP shouldn't be used without CONFIG_SMP, so we can
> safely
> add this dependency.
> Ingo's suggestion will still fix unreferenced variables warnings, so how
> about the following patch?
>
> Thanks,
> Ido.
>
> From 6fa023be44749092088618379f13d7a3e086d692 Mon Sep 17 00:00:00
> 2001
> From: Shai Fultheim <shai@...lemp.com>
> Date: Mon, 16 Apr 2012 10:39:35 +0300
> Subject: [PATCH v5] vsmp: Fix number of CPUs when vsmp is disabled
>
> In case CONFIG_X86_VSMP is not set, limit the number of CPUs to the
> number of CPUs of the first board.
>
> Also make CONFIG_X86_VSMP depend on CONFIG_SMP, as there's little
> point in having a vsmp machine with a single CPU.
>
> Signed-off-by: Shai Fultheim <shai@...lemp.com>
> [ido@...ery.com: rebased, fixed minor coding-style issues]
> Signed-off-by: Ido Yariv <ido@...ery.com>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/vsmp_64.c | 40
> ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 41 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c9866b0..b1e98c9 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -374,6 +374,7 @@ config X86_VSMP
> select PARAVIRT
> depends on X86_64 && PCI
> depends on X86_EXTENDED_PLATFORM
> + depends on SMP
> ---help---
> Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
> supposed to run on these EM64T-based machines. Only choose this
> option
> diff --git a/arch/x86/kernel/vsmp_64.c b/arch/x86/kernel/vsmp_64.c
> index a1d804b..8eeb55a 100644
> --- a/arch/x86/kernel/vsmp_64.c
> +++ b/arch/x86/kernel/vsmp_64.c
> @@ -15,6 +15,7 @@
> #include <linux/init.h>
> #include <linux/pci_ids.h>
> #include <linux/pci_regs.h>
> +#include <linux/smp.h>
>
> #include <asm/apic.h>
> #include <asm/pci-direct.h>
> @@ -22,6 +23,8 @@
> #include <asm/paravirt.h>
> #include <asm/setup.h>
>
> +#define TOPOLOGY_REGISTER_OFFSET 0x10
> +
> #if defined CONFIG_PCI && defined CONFIG_PARAVIRT
> /*
> * Interrupt control on vSMPowered systems:
> @@ -149,12 +152,49 @@ int is_vsmp_box(void)
> return 0;
> }
> #endif
> +
> +static void __init vsmp_cap_cpus(void)
> +{
> +#if !defined(CONFIG_X86_VSMP) && defined(CONFIG_SMP)
> + void __iomem *address;
> + unsigned int cfg, topology, node_shift, maxcpus;
> +
> + /*
> + * CONFIG_X86_VSMP is not configured, so limit the number CPUs to
> the
> + * ones present in the first board, unless explicitly overridden by
> + * setup_max_cpus
> + */
> + if (setup_max_cpus != NR_CPUS)
> + return;
> +
> + /* Read the vSMP Foundation topology register */
> + cfg = read_pci_config(0, 0x1f, 0, PCI_BASE_ADDRESS_0);
> + address = early_ioremap(cfg + TOPOLOGY_REGISTER_OFFSET, 4);
> + if (WARN_ON(!address))
> + return;
> +
> + topology = readl(address);
> + node_shift = (topology >> 16) & 0x7;
> + if (!node_shift)
> + /* The value 0 should be decoded as 8 */
> + node_shift = 8;
> + maxcpus = (topology & ((1 << node_shift) - 1)) + 1;
> +
> + pr_info("vSMP CTL: Capping CPUs to %d (CONFIG_X86_VSMP is
> unset)\n",
> + maxcpus);
> + setup_max_cpus = maxcpus;
> + early_iounmap(address, 4);
> +#endif
> +}
> +
> void __init vsmp_init(void)
> {
> detect_vsmp_box();
> if (!is_vsmp_box())
> return;
>
> + vsmp_cap_cpus();
> +
> set_vsmp_pv_ops();
> return;
> }
> --
> 1.7.6.5
--
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