[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] arm: don't use atomic operations to gate non-boot CPUs
On Thu, 2012-03-15 at 14:15 +0000, Tim Deegan wrote: > # 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> Committed, thanks. (do we care about trailing whitespace? there was some, "git am" warns me...) > > 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: _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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