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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] arm: don't use atomic operations to gate non-boot CPUs
# HG changeset patch
# User Tim Deegan <tim@xxxxxxx>
# Date 1331820837 0
# Node ID 6f52e5de1b942432ffa6c3b8d194e5e2771c1957
# Parent 4da1453ed61c28a366162b49b2f59f62e070a799
arm: don't use atomic operations to gate non-boot CPUs.
Since the cache is not enabled that early, better not to rely on
load-linked/store-conditional. Instead, have the boot CPU call the
other CPUs by their IDs, just like we do later for proper CPU bringup.
Signed-off-by: Tim Deegan <tim@xxxxxxx>
diff -r 4da1453ed61c -r 6f52e5de1b94 xen/arch/arm/head.S
--- a/xen/arch/arm/head.S Thu Mar 15 11:47:27 2012 +0000
+++ b/xen/arch/arm/head.S Thu Mar 15 14:13:57 2012 +0000
@@ -71,16 +71,13 @@ start:
bics r12, r0, #(0xff << 24) /* Mask out flags to get CPU ID */
beq boot_cpu /* If we're CPU 0, boot now */
- /* Non-boot CPUs wait here to be woken up one at a time.
- * This is basically an open-coded spin-lock to serialize. */
- ldr r0, =boot_gate /* VA of gate */
+ /* Non-boot CPUs wait here to be woken up one at a time. */
+1: wfe
+ dsb
+ ldr r0, =smp_up_cpu /* VA of gate */
add r0, r0, r10 /* PA of gate */
- mov r1, #1 /* (1 == locked) */
-1: wfe
- ldrex r2, [r0] /* Linked read of current value */
- teq r2, #0 /* (0 == unlocked) */
- strexeq r2, r1, [r0] /* Matching update -> locked */
- teq r2, #0 /* (0 == succeeded) */
+ ldr r1, [r0] /* Which CPU is being booted? */
+ teq r1, r12 /* Is it us? */
bne 1b
boot_cpu:
@@ -270,16 +267,7 @@ paging:
teq r12, #0
beq launch
- /* Signal the next non-boot CPU to come and join us here */
- ldr r0, =boot_gate /* VA of gate */
- add r0, r0, r10 /* PA of gate */
- mov r1, #0 /* (0 == unlocked) */
- str r1, [r0]
- dsb
- isb
- sev
-
- /* Move on to the relocated pagetables */
+ /* Non-boot CPUs need to move on to the relocated pagetables */
mov r0, #0
ldr r4, =boot_httbr /* VA of HTTBR value stashed by CPU 0 */
add r4, r4, r10 /* PA of it */
diff -r 4da1453ed61c -r 6f52e5de1b94 xen/arch/arm/setup.c
--- a/xen/arch/arm/setup.c Thu Mar 15 11:47:27 2012 +0000
+++ b/xen/arch/arm/setup.c Thu Mar 15 14:13:57 2012 +0000
@@ -38,11 +38,6 @@
#include <asm/setup.h>
#include "gic.h"
-/* Spinlock for serializing CPU bringup */
-unsigned long __initdata boot_gate = 1;
-/* Number of non-boot CPUs ready to enter C */
-unsigned long __initdata ready_cpus = 0;
-
static __attribute_used__ void init_done(void)
{
free_init_memory();
@@ -152,8 +147,6 @@ void __init start_xen(unsigned long boot
void *fdt;
size_t fdt_size;
int cpus, i;
- paddr_t gate_pa;
- unsigned long *gate;
fdt = (void *)BOOT_MISC_VIRT_START
+ (atag_paddr & ((1 << SECOND_SHIFT) - 1));
@@ -169,25 +162,11 @@ void __init start_xen(unsigned long boot
console_init_preirq();
#endif
+ cpus = gic_init();
+ make_cpus_ready(cpus, boot_phys_offset);
+
percpu_init_areas();
set_processor_id(0); /* needed early, for smp_processor_id() */
-
- cpus = gic_init();
-
- printk("Waiting for %i other CPUs to be ready\n", cpus - 1);
- /* Bring the other CPUs up to paging before the original
- * copy of .text gets overwritten. We need to use the unrelocated
- * copy of boot_gate as that's the one the others can see. */
- gate_pa = ((unsigned long) &boot_gate) + boot_phys_offset;
- gate = map_domain_page(gate_pa >> PAGE_SHIFT) + (gate_pa & ~PAGE_MASK);
- *gate = 0;
- unmap_domain_page(gate);
- /* Now send an event to wake the first non-boot CPU */
- asm volatile("dsb; isb; sev");
- /* And wait for them all to be ready. */
- while ( ready_cpus + 1 < cpus )
- smp_rmb();
-
__set_current((struct vcpu *)0xfffff000); /* debug sanity */
idle_vcpu[0] = current;
diff -r 4da1453ed61c -r 6f52e5de1b94 xen/arch/arm/smpboot.c
--- a/xen/arch/arm/smpboot.c Thu Mar 15 11:47:27 2012 +0000
+++ b/xen/arch/arm/smpboot.c Thu Mar 15 14:13:57 2012 +0000
@@ -19,6 +19,7 @@
#include <xen/cpu.h>
#include <xen/cpumask.h>
#include <xen/delay.h>
+#include <xen/domain_page.h>
#include <xen/errno.h>
#include <xen/init.h>
#include <xen/mm.h>
@@ -41,11 +42,17 @@ static unsigned char __initdata cpu0_boo
/* Pointer to the stack, used by head.S when entering C */
unsigned char *init_stack = cpu0_boot_stack;
+/* Shared state for coordinating CPU bringup */
+unsigned long smp_up_cpu = 0;
+static bool_t cpu_is_dead = 0;
+
+/* Number of non-boot CPUs ready to enter C */
+unsigned long __initdata ready_cpus = 0;
+
void __init
smp_prepare_cpus (unsigned int max_cpus)
{
int i;
- set_processor_id(0); /* needed early, for smp_processor_id() */
cpumask_clear(&cpu_online_map);
cpumask_set_cpu(0, &cpu_online_map);
@@ -56,9 +63,30 @@ smp_prepare_cpus (unsigned int max_cpus)
cpumask_copy(&cpu_present_map, &cpu_possible_map);
}
-/* Shared state for coordinating CPU bringup */
-unsigned long smp_up_cpu = 0;
-static bool_t cpu_is_dead = 0;
+void __init
+make_cpus_ready(unsigned int max_cpus, unsigned long boot_phys_offset)
+{
+ unsigned long *gate;
+ paddr_t gate_pa;
+ int i;
+
+ printk("Waiting for %i other CPUs to be ready\n", max_cpus - 1);
+ /* We use the unrelocated copy of smp_up_cpu as that's the one the
+ * others can see. */
+ gate_pa = ((paddr_t) (unsigned long) &smp_up_cpu) + boot_phys_offset;
+ gate = map_domain_page(gate_pa >> PAGE_SHIFT) + (gate_pa & ~PAGE_MASK);
+ for ( i = 1; i < max_cpus; i++ )
+ {
+ /* Tell the next CPU to get ready */
+ /* TODO: handle boards where CPUIDs are not contiguous */
+ *gate = i;
+ asm volatile("dsb; isb; sev");
+ /* And wait for it to respond */
+ while ( ready_cpus < i )
+ smp_rmb();
+ }
+ unmap_domain_page(gate);
+}
/* Boot the current CPU */
void __cpuinit start_secondary(unsigned long boot_phys_offset,
diff -r 4da1453ed61c -r 6f52e5de1b94 xen/include/asm-arm/smp.h
--- a/xen/include/asm-arm/smp.h Thu Mar 15 11:47:27 2012 +0000
+++ b/xen/include/asm-arm/smp.h Thu Mar 15 14:13:57 2012 +0000
@@ -16,6 +16,12 @@ DECLARE_PER_CPU(cpumask_var_t, cpu_core_
extern void stop_cpu(void);
+/* Bring the non-boot CPUs up to paging and ready to enter C.
+ * Must be called after Xen is relocated but before the original copy of
+ * .text gets overwritten. */
+extern void
+make_cpus_ready(unsigned int max_cpus, unsigned long boot_phys_offset);
+
#endif
/*
* Local variables:
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