Re: [Xen-devel] [PATCH 4 of 9] arm: per-cpu areas

[Tim Deegan <tim@xxxxxxx>]

Hold off on this - it seems to mess up context switches (something to so
with current being a per-cpu variable and per-cpu variables being
accessed via the current vcpu's stack...)

Tim.

At 13:43 +0000 on 09 Mar (1331300613), Tim Deegan wrote:
> # HG changeset patch
> # User Tim Deegan <tim@xxxxxxx>
> # Date 1331300346 0
> # Node ID ded775f8a1278c98d8341338b47df0700992e01b
> # Parent  ef66ce0f4fb3bfe72acd691e4db33f0c1ea9137d
> arm: per-cpu areas
> 
> Signed-off-by: Tim Deegan <tim@xxxxxxx>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> 
> diff -r ef66ce0f4fb3 -r ded775f8a127 xen/arch/arm/Makefile
> --- a/xen/arch/arm/Makefile   Fri Mar 09 13:39:06 2012 +0000
> +++ b/xen/arch/arm/Makefile   Fri Mar 09 13:39:06 2012 +0000
> @@ -13,6 +13,7 @@ obj-y += irq.o
>  obj-y += kernel.o
>  obj-y += mm.o
>  obj-y += p2m.o
> +obj-y += percpu.o
>  obj-y += guestcopy.o
>  obj-y += setup.o
>  obj-y += time.o
> diff -r ef66ce0f4fb3 -r ded775f8a127 xen/arch/arm/dummy.S
> --- a/xen/arch/arm/dummy.S    Fri Mar 09 13:39:06 2012 +0000
> +++ b/xen/arch/arm/dummy.S    Fri Mar 09 13:39:06 2012 +0000
> @@ -14,7 +14,6 @@ DUMMY(per_cpu__cpu_core_mask);
>  DUMMY(per_cpu__cpu_sibling_mask);
>  DUMMY(node_online_map);
>  DUMMY(smp_send_state_dump);
> -DUMMY(__per_cpu_offset);
>  
>  /* PIRQ support */
>  DUMMY(alloc_pirq_struct);
> diff -r ef66ce0f4fb3 -r ded775f8a127 xen/arch/arm/percpu.c
> --- /dev/null Thu Jan 01 00:00:00 1970 +0000
> +++ b/xen/arch/arm/percpu.c   Fri Mar 09 13:39:06 2012 +0000
> @@ -0,0 +1,85 @@
> +#include <xen/config.h>
> +#include <xen/percpu.h>
> +#include <xen/cpu.h>
> +#include <xen/init.h>
> +#include <xen/mm.h>
> +#include <xen/rcupdate.h>
> +
> +unsigned long __per_cpu_offset[NR_CPUS];
> +#define INVALID_PERCPU_AREA (-(long)__per_cpu_start)
> +#define PERCPU_ORDER 
> (get_order_from_bytes(__per_cpu_data_end-__per_cpu_start))
> +
> +void __init percpu_init_areas(void)
> +{
> +    unsigned int cpu;
> +    for ( cpu = 1; cpu < NR_CPUS; cpu++ )
> +        __per_cpu_offset[cpu] = INVALID_PERCPU_AREA;
> +}
> +
> +static int init_percpu_area(unsigned int cpu)
> +{
> +    char *p;
> +    if ( __per_cpu_offset[cpu] != INVALID_PERCPU_AREA )
> +        return -EBUSY;
> +    if ( (p = alloc_xenheap_pages(PERCPU_ORDER, 0)) == NULL )
> +        return -ENOMEM;
> +    memset(p, 0, __per_cpu_data_end - __per_cpu_start);
> +    __per_cpu_offset[cpu] = p - __per_cpu_start;
> +    return 0;
> +}
> +
> +struct free_info {
> +    unsigned int cpu;
> +    struct rcu_head rcu;
> +};
> +static DEFINE_PER_CPU(struct free_info, free_info);
> +
> +static void _free_percpu_area(struct rcu_head *head)
> +{
> +    struct free_info *info = container_of(head, struct free_info, rcu);
> +    unsigned int cpu = info->cpu;
> +    char *p = __per_cpu_start + __per_cpu_offset[cpu];
> +    free_xenheap_pages(p, PERCPU_ORDER);
> +    __per_cpu_offset[cpu] = INVALID_PERCPU_AREA;
> +}
> +
> +static void free_percpu_area(unsigned int cpu)
> +{
> +    struct free_info *info = &per_cpu(free_info, cpu);
> +    info->cpu = cpu;
> +    call_rcu(&info->rcu, _free_percpu_area);
> +}
> +
> +static int cpu_percpu_callback(
> +    struct notifier_block *nfb, unsigned long action, void *hcpu)
> +{
> +    unsigned int cpu = (unsigned long)hcpu;
> +    int rc = 0;
> +
> +    switch ( action )
> +    {
> +    case CPU_UP_PREPARE:
> +        rc = init_percpu_area(cpu);
> +        break;
> +    case CPU_UP_CANCELED:
> +    case CPU_DEAD:
> +        free_percpu_area(cpu);
> +        break;
> +    default:
> +        break;
> +    }
> +
> +    return !rc ? NOTIFY_DONE : notifier_from_errno(rc);
> +}
> +
> +static struct notifier_block cpu_percpu_nfb = {
> +    .notifier_call = cpu_percpu_callback,
> +    .priority = 100 /* highest priority */
> +};
> +
> +static int __init percpu_presmp_init(void)
> +{
> +    register_cpu_notifier(&cpu_percpu_nfb);
> +    return 0;
> +}
> +presmp_initcall(percpu_presmp_init);
> diff -r ef66ce0f4fb3 -r ded775f8a127 xen/include/asm-arm/percpu.h
> --- a/xen/include/asm-arm/percpu.h    Fri Mar 09 13:39:06 2012 +0000
> +++ b/xen/include/asm-arm/percpu.h    Fri Mar 09 13:39:06 2012 +0000
> @@ -12,8 +12,11 @@ void percpu_init_areas(void);
>      __attribute__((__section__(".bss.percpu" #suffix)))         \
>      __typeof__(type) per_cpu_##name
>  
> -#define per_cpu(var, cpu) ((&per_cpu__##var)[cpu?0:0])
> -#define __get_cpu_var(var) per_cpu__##var
> +
> +#define per_cpu(var, cpu)  \
> +    (*RELOC_HIDE(&per_cpu__##var, __per_cpu_offset[cpu]))
> +#define __get_cpu_var(var) \
> +    (*RELOC_HIDE(&per_cpu__##var, get_cpu_info()->per_cpu_offset))
>  
>  #define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu__##name
>  
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel