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

On 18/12/12 12:19, Stefano Stabellini wrote:

On Mon, 17 Dec 2012, Will Deacon wrote:

quoted

This patch adds support for SMP to mach-virt using the PSCI
infrastructure.

Signed-off-by: Will Deacon <redacted>

 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?

Well, I was considering using it to "power-off" the VM when the last CPU
powers itself off, and this would apply to UP as well.

quoted

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@arm.com>
+ *
+ * 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?

All methods are optional, so I'm afraid you have to check for their
validity each time you want to access one.

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

quoted

+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

-- 
Jazz is not dead. It just smells funny...