Re: [Xen-devel] [PATCH v2 6/6] ARM: mach-virt: add SMP support using PSCI

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 17 Dec 2012, Will Deacon wrote:
> This patch adds support for SMP to mach-virt using the PSCI
> infrastructure.
> 
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
>
>  arch/arm/mach-virt/Kconfig   |  1 +
>  arch/arm/mach-virt/Makefile  |  1 +
>  arch/arm/mach-virt/platsmp.c | 76 
> ++++++++++++++++++++++++++++++++++++++++++++
>  arch/arm/mach-virt/virt.c    |  6 ++++
>  4 files changed, 84 insertions(+)
>  create mode 100644 arch/arm/mach-virt/platsmp.c
> 
> diff --git a/arch/arm/mach-virt/Kconfig b/arch/arm/mach-virt/Kconfig
> index a568a2a..8958f0d 100644
> --- a/arch/arm/mach-virt/Kconfig
> +++ b/arch/arm/mach-virt/Kconfig
> @@ -3,6 +3,7 @@ config ARCH_VIRT
>       select ARCH_WANT_OPTIONAL_GPIOLIB
>       select ARM_GIC
>       select ARM_ARCH_TIMER
> +     select ARM_PSCI
>       select HAVE_SMP
>       select CPU_V7
>       select SPARSE_IRQ

Considering that PSCI is actually needed only to boot secondary cpus,
maybe we want to select it if CONFIG_SMP is enabled?


> diff --git a/arch/arm/mach-virt/Makefile b/arch/arm/mach-virt/Makefile
> index 7ddbfa6..042afc1 100644
> --- a/arch/arm/mach-virt/Makefile
> +++ b/arch/arm/mach-virt/Makefile
> @@ -3,3 +3,4 @@
>  #
>  
>  obj-y                                        := virt.o
> +obj-$(CONFIG_SMP)                    += platsmp.o
> diff --git a/arch/arm/mach-virt/platsmp.c b/arch/arm/mach-virt/platsmp.c
> new file mode 100644
> index 0000000..930362b
> --- /dev/null
> +++ b/arch/arm/mach-virt/platsmp.c
> @@ -0,0 +1,76 @@
> +/*
> + * Dummy Virtual Machine - does what it says on the tin.
> + *
> + * Copyright (C) 2012 ARM Ltd
> + * Author: Will Deacon <will.deacon@xxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/smp.h>
> +#include <linux/of.h>
> +
> +#include <asm/psci.h>
> +#include <asm/smp_plat.h>
> +#include <asm/hardware/gic.h>
> +
> +extern void secondary_startup(void);
> +
> +/*
> + * Enumerate the possible CPU set from the device tree.
> + */
> +static void __init virt_smp_init_cpus(void)
> +{
> +     struct device_node *dn = NULL;
> +     int cpu = 0;
> +
> +     while ((dn = of_find_node_by_type(dn, "cpu"))) {
> +             if (cpu < NR_CPUS)
> +                     set_cpu_possible(cpu, true);
> +             cpu++;
> +     }
> +
> +     /* sanity check */
> +     if (cpu > NR_CPUS)
> +             pr_warning("no. of cores (%d) greater than configured maximum "
> +                        "of %d - clipping\n",
> +                        cpu, NR_CPUS);
> +
> +     set_smp_cross_call(gic_raise_softirq);
> +}
> +
> +static void __init virt_smp_prepare_cpus(unsigned int max_cpus)
> +{
> +}
> +
> +static int __cpuinit virt_boot_secondary(unsigned int cpu,
> +                                      struct task_struct *idle)
> +{
> +     if (psci_ops.cpu_on)
> +             return psci_ops.cpu_on(cpu_logical_map(cpu),
> +                                    __pa(secondary_startup));
> +     return -ENODEV;
> +}

Isn't there a better way to check whether PSCI is actually "enabled", as
in present in the device tree and initialized correctly?

Maybe we need a pcsi_enabled() static inline of some sort?


> +static void __cpuinit virt_secondary_init(unsigned int cpu)
> +{
> +     gic_secondary_init(0);
> +}
> +
> +struct smp_operations __initdata virt_smp_ops = {
> +     .smp_init_cpus          = virt_smp_init_cpus,
> +     .smp_prepare_cpus       = virt_smp_prepare_cpus,
> +     .smp_secondary_init     = virt_secondary_init,
> +     .smp_boot_secondary     = virt_boot_secondary,
> +};
> diff --git a/arch/arm/mach-virt/virt.c b/arch/arm/mach-virt/virt.c
> index 174b9da..d764835 100644
> --- a/arch/arm/mach-virt/virt.c
> +++ b/arch/arm/mach-virt/virt.c
> @@ -20,6 +20,7 @@
>  
>  #include <linux/of_irq.h>
>  #include <linux/of_platform.h>
> +#include <linux/smp.h>
>  
>  #include <asm/arch_timer.h>
>  #include <asm/hardware/gic.h>
> @@ -56,10 +57,15 @@ static struct sys_timer virt_timer = {
>       .init = virt_timer_init,
>  };
>  
> +#ifdef CONFIG_SMP
> +extern struct smp_operations virt_smp_ops;
> +#endif
> +
>  DT_MACHINE_START(VIRT, "Dummy Virtual Machine")
>       .init_irq       = gic_init_irq,
>       .handle_irq     = gic_handle_irq,
>       .timer          = &virt_timer,
>       .init_machine   = virt_init,
> +     .smp            = smp_ops(virt_smp_ops),
>       .dt_compat      = virt_dt_match,
>  MACHINE_END
> -- 
> 1.8.0

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