[PATCH v6 (proposal)] powerpc/cpu: enable nr_cpus for crash kernel

Pingfan Liu piliu at redhat.com
Tue Jan 30 18:28:18 AEDT 2024


Hi Christophe,

The latest series is
https://lore.kernel.org/linuxppc-dev/20231017022806.4523-1-piliu@redhat.com/

And Michael has his implement on:
https://lore.kernel.org/all/20231229120107.2281153-3-mpe@ellerman.id.au/T/#m46128446bce1095631162a1927415733a3bf0633

Thanks,

Pingfan

On Fri, Jan 26, 2024 at 3:40 AM Christophe Leroy
<christophe.leroy at csgroup.eu> wrote:
>
> Hi,
>
> Le 22/05/2018 à 10:23, Pingfan Liu a écrit :
> > For kexec -p, the boot cpu can be not the cpu0, this causes the problem
> > to alloc paca[]. In theory, there is no requirement to assign cpu's logical
> > id as its present seq by device tree. But we have something like
> > cpu_first_thread_sibling(), which makes assumption on the mapping inside
> > a core. Hence partially changing the mapping, i.e. unbind the mapping of
> > core while keep the mapping inside a core. After this patch, the core with
> > boot-cpu will always be mapped into core 0.
> >
> > And at present, the code to discovery cpu spreads over two functions:
> > early_init_dt_scan_cpus() and smp_setup_cpu_maps().
> > This patch tries to fold smp_setup_cpu_maps() into the "previous" one
>
> This patch is pretty old and doesn't apply anymore. If still relevant
> can you please rebase and resubmit.
>
> Thanks
> Christophe
>
> >
> > Signed-off-by: Pingfan Liu <kernelfans at gmail.com>
> > ---
> > v5 -> v6:
> >    simplify the loop logic (Hope it can answer Benjamin's concern)
> >    concentrate the cpu recovery code to early stage (Hope it can answer Michael's concern)
> > Todo: (if this method is accepted)
> >    fold the whole smp_setup_cpu_maps()
> >
> >   arch/powerpc/include/asm/smp.h     |   1 +
> >   arch/powerpc/kernel/prom.c         | 123 ++++++++++++++++++++++++++++---------
> >   arch/powerpc/kernel/setup-common.c |  58 ++---------------
> >   drivers/of/fdt.c                   |   2 +-
> >   include/linux/of_fdt.h             |   2 +
> >   5 files changed, 103 insertions(+), 83 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
> > index fac963e..80c7693 100644
> > --- a/arch/powerpc/include/asm/smp.h
> > +++ b/arch/powerpc/include/asm/smp.h
> > @@ -30,6 +30,7 @@
> >   #include <asm/percpu.h>
> >
> >   extern int boot_cpuid;
> > +extern int threads_in_core;
> >   extern int spinning_secondaries;
> >
> >   extern void cpu_die(void);
> > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> > index 4922162..2ae0b4a 100644
> > --- a/arch/powerpc/kernel/prom.c
> > +++ b/arch/powerpc/kernel/prom.c
> > @@ -77,7 +77,6 @@ unsigned long tce_alloc_start, tce_alloc_end;
> >   u64 ppc64_rma_size;
> >   #endif
> >   static phys_addr_t first_memblock_size;
> > -static int __initdata boot_cpu_count;
> >
> >   static int __init early_parse_mem(char *p)
> >   {
> > @@ -305,6 +304,14 @@ static void __init check_cpu_feature_properties(unsigned long node)
> >       }
> >   }
> >
> > +struct bootinfo {
> > +     int boot_thread_id;
> > +     unsigned int cpu_cnt;
> > +     int cpu_hwids[NR_CPUS];
> > +     bool avail[NR_CPUS];
> > +};
> > +static struct bootinfo *bt_info;
> > +
> >   static int __init early_init_dt_scan_cpus(unsigned long node,
> >                                         const char *uname, int depth,
> >                                         void *data)
> > @@ -312,10 +319,12 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
> >       const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> >       const __be32 *prop;
> >       const __be32 *intserv;
> > -     int i, nthreads;
> > +     int i, nthreads, maxidx;
> >       int len;
> > -     int found = -1;
> > -     int found_thread = 0;
> > +     int found_thread = -1;
> > +     struct bootinfo *info = data;
> > +     bool avail;
> > +     int rotate_cnt, id;
> >
> >       /* We are scanning "cpu" nodes only */
> >       if (type == NULL || strcmp(type, "cpu") != 0)
> > @@ -325,8 +334,15 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
> >       intserv = of_get_flat_dt_prop(node, "ibm,ppc-interrupt-server#s", &len);
> >       if (!intserv)
> >               intserv = of_get_flat_dt_prop(node, "reg", &len);
> > +     avail = of_fdt_device_is_available(initial_boot_params, node);
> > +#if 0
> > +     //todo
> > +     if (!avail)
> > +             avail = !of_fdt_property_match_string(node,
> > +                                     "enable-method", "spin-table");
> > +#endif
> >
> > -     nthreads = len / sizeof(int);
> > +     threads_in_core = nthreads = len / sizeof(int);
> >
> >       /*
> >        * Now see if any of these threads match our boot cpu.
> > @@ -338,9 +354,10 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
> >                * booted proc.
> >                */
> >               if (fdt_version(initial_boot_params) >= 2) {
> > +                     info->cpu_hwids[info->cpu_cnt] =
> > +                                     be32_to_cpu(intserv[i]);
> >                       if (be32_to_cpu(intserv[i]) ==
> >                           fdt_boot_cpuid_phys(initial_boot_params)) {
> > -                             found = boot_cpu_count;
> >                               found_thread = i;
> >                       }
> >               } else {
> > @@ -351,22 +368,37 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
> >                        */
> >                       if (of_get_flat_dt_prop(node,
> >                                       "linux,boot-cpu", NULL) != NULL)
> > -                             found = boot_cpu_count;
> > +                             found_thread = info->cpu_cnt;
> >               }
> > +             info->avail[info->cpu_cnt] = avail;
> > +
> >   #ifdef CONFIG_SMP
> >               /* logical cpu id is always 0 on UP kernels */
> > -             boot_cpu_count++;
> > +             info->cpu_cnt++;
> >   #endif
> >       }
> >
> >       /* Not the boot CPU */
> > -     if (found < 0)
> > +     if (found_thread < 0)
> >               return 0;
> >
> > -     DBG("boot cpu: logical %d physical %d\n", found,
> > +     /* always mapping boot-core to core 0 to cope with kexec -p */
> > +     maxidx = info->cpu_cnt - 1;
> > +     rotate_cnt = nthreads;
> > +     while (rotate_cnt-- > 0) {
> > +             avail = info->avail[maxidx];
> > +             id = info->cpu_hwids[maxidx];
> > +             for (i = maxidx; i > 0; i--) {
> > +                     info->avail[i] = info->avail[i - 1];
> > +                     info->cpu_hwids[i] = info->cpu_hwids[i - 1];
> > +             }
> > +             info->avail[i] = avail;
> > +             info->cpu_hwids[i] = id;
> > +     }
> > +
> > +     info->boot_thread_id = found_thread;
> > +     DBG("boot cpu: logical %d physical %d\n", found_thread,
> >           be32_to_cpu(intserv[found_thread]));
> > -     boot_cpuid = found;
> > -     set_hard_smp_processor_id(found, be32_to_cpu(intserv[found_thread]));
> >
> >       /*
> >        * PAPR defines "logical" PVR values for cpus that
> > @@ -675,6 +707,55 @@ static void __init tm_init(void)
> >   static void tm_init(void) { }
> >   #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
> >
> > +static void early_setup_cpu_mapping(void)
> > +{
> > +     unsigned int cpu, cnt;
> > +     int nr_cpus_aligned;
> > +
> > +     bt_info = __va(memblock_alloc(sizeof(struct bootinfo),
> > +                     sizeof(unsigned long)));
> > +     memset(bt_info, 0, sizeof(struct bootinfo));
> > +     bt_info->boot_thread_id = -1;
> > +     /* Retrieve CPU related informations from the flat tree
> > +      * (altivec support, boot CPU ID, ...)
> > +      */
> > +     of_scan_flat_dt(early_init_dt_scan_cpus, bt_info);
> > +
> > +     if (bt_info->boot_thread_id < 0) {
> > +             pr_err("Failed to identify boot CPU !\n");
> > +             BUG();
> > +     }
> > +
> > +     boot_cpuid = bt_info->boot_thread_id;
> > +     /* work around subcore mode */
> > +     nr_cpus_aligned = _ALIGN_UP(nr_cpu_ids, threads_in_core);
> > +     if (nr_cpus_aligned != nr_cpu_ids) {
> > +             pr_info("nr_cpus is forced to be aligned up from: %d to: %d\n",
> > +                     nr_cpu_ids, nr_cpus_aligned);
> > +             nr_cpu_ids = nr_cpus_aligned;
> > +     }
> > +     cnt = (nr_cpu_ids < bt_info->cpu_cnt) ? nr_cpu_ids
> > +                     : bt_info->cpu_cnt;
> > +
> > +     allocate_pacas();
> > +     for (cpu = 0; cpu < cnt; cpu++) {
> > +             set_cpu_present(cpu, bt_info->avail[cpu]);
> > +             DBG("set cpu present: %d -> hwid:%d\n",
> > +                     cpu, bt_info->cpu_hwids[cpu]);
> > +             set_hard_smp_processor_id(cpu, bt_info->cpu_hwids[cpu]);
> > +             set_cpu_possible(cpu, true);
> > +     }
> > +
> > +#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
> > +     /* We'll later wait for secondaries to check in; there are
> > +      * NCPUS-1 non-boot CPUs  :-)
> > +      */
> > +     spinning_secondaries = bt_info->cpu_cnt - 1;
> > +#endif
> > +     memblock_free(__pa(bt_info), sizeof(struct bootinfo));
> > +     bt_info = NULL;
> > +}
> > +
> >   void __init early_init_devtree(void *params)
> >   {
> >       phys_addr_t limit;
> > @@ -745,27 +826,11 @@ void __init early_init_devtree(void *params)
> >        * FIXME .. and the initrd too? */
> >       move_device_tree();
> >
> > -     allocate_pacas();
> > -
> >       DBG("Scanning CPUs ...\n");
> >
> >       dt_cpu_ftrs_scan();
> >
> > -     /* Retrieve CPU related informations from the flat tree
> > -      * (altivec support, boot CPU ID, ...)
> > -      */
> > -     of_scan_flat_dt(early_init_dt_scan_cpus, NULL);
> > -     if (boot_cpuid < 0) {
> > -             printk("Failed to identify boot CPU !\n");
> > -             BUG();
> > -     }
> > -
> > -#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
> > -     /* We'll later wait for secondaries to check in; there are
> > -      * NCPUS-1 non-boot CPUs  :-)
> > -      */
> > -     spinning_secondaries = boot_cpu_count - 1;
> > -#endif
> > +     early_setup_cpu_mapping();
> >
> >       mmu_early_init_devtree();
> >
> > diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
> > index 66f7cc6..46d034a 100644
> > --- a/arch/powerpc/kernel/setup-common.c
> > +++ b/arch/powerpc/kernel/setup-common.c
> > @@ -86,7 +86,9 @@ struct machdep_calls *machine_id;
> >   EXPORT_SYMBOL(machine_id);
> >
> >   int boot_cpuid = -1;
> > +int threads_in_core = 1;
> >   EXPORT_SYMBOL_GPL(boot_cpuid);
> > +EXPORT_SYMBOL_GPL(threads_in_core);
> >
> >   /*
> >    * These are used in binfmt_elf.c to put aux entries on the stack
> > @@ -460,61 +462,11 @@ void __init smp_setup_cpu_maps(void)
> >   {
> >       struct device_node *dn;
> >       int cpu = 0;
> > -     int nthreads = 1;
> > -
> > -     DBG("smp_setup_cpu_maps()\n");
> > -
> > -     for_each_node_by_type(dn, "cpu") {
> > -             const __be32 *intserv;
> > -             __be32 cpu_be;
> > -             int j, len;
> > -
> > -             DBG("  * %pOF...\n", dn);
> > -
> > -             intserv = of_get_property(dn, "ibm,ppc-interrupt-server#s",
> > -                             &len);
> > -             if (intserv) {
> > -                     DBG("    ibm,ppc-interrupt-server#s -> %d threads\n",
> > -                         nthreads);
> > -             } else {
> > -                     DBG("    no ibm,ppc-interrupt-server#s -> 1 thread\n");
> > -                     intserv = of_get_property(dn, "reg", &len);
> > -                     if (!intserv) {
> > -                             cpu_be = cpu_to_be32(cpu);
> > -                             intserv = &cpu_be;      /* assume logical == phys */
> > -                             len = 4;
> > -                     }
> > -             }
> > -
> > -             nthreads = len / sizeof(int);
> > -
> > -             for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
> > -                     bool avail;
> > -
> > -                     DBG("    thread %d -> cpu %d (hard id %d)\n",
> > -                         j, cpu, be32_to_cpu(intserv[j]));
> > -
> > -                     avail = of_device_is_available(dn);
> > -                     if (!avail)
> > -                             avail = !of_property_match_string(dn,
> > -                                             "enable-method", "spin-table");
> > -
> > -                     set_cpu_present(cpu, avail);
> > -                     set_hard_smp_processor_id(cpu, be32_to_cpu(intserv[j]));
> > -                     set_cpu_possible(cpu, true);
> > -                     cpu++;
> > -             }
> > -
> > -             if (cpu >= nr_cpu_ids) {
> > -                     of_node_put(dn);
> > -                     break;
> > -             }
> > -     }
> >
> >       /* If no SMT supported, nthreads is forced to 1 */
> >       if (!cpu_has_feature(CPU_FTR_SMT)) {
> >               DBG("  SMT disabled ! nthreads forced to 1\n");
> > -             nthreads = 1;
> > +             threads_in_core = 1;
> >       }
> >
> >   #ifdef CONFIG_PPC64
> > @@ -539,7 +491,7 @@ void __init smp_setup_cpu_maps(void)
> >
> >               /* Double maxcpus for processors which have SMT capability */
> >               if (cpu_has_feature(CPU_FTR_SMT))
> > -                     maxcpus *= nthreads;
> > +                     maxcpus *= threads_in_core;
> >
> >               if (maxcpus > nr_cpu_ids) {
> >                       printk(KERN_WARNING
> > @@ -565,7 +517,7 @@ void __init smp_setup_cpu_maps(void)
> >        * every CPU in the system. If that is not the case, then some code
> >        * here will have to be reworked
> >        */
> > -     cpu_init_thread_core_maps(nthreads);
> > +     cpu_init_thread_core_maps(threads_in_core);
> >
> >       /* Now that possible cpus are set, set nr_cpu_ids for later use */
> >       setup_nr_cpu_ids();
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index 84aa9d6..16d6b02 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -130,7 +130,7 @@ bool of_fdt_is_big_endian(const void *blob, unsigned long node)
> >       return false;
> >   }
> >
> > -static bool of_fdt_device_is_available(const void *blob, unsigned long node)
> > +bool of_fdt_device_is_available(const void *blob, unsigned long node)
> >   {
> >       const char *status = fdt_getprop(blob, node, "status", NULL);
> >
> > diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> > index b9cd9eb..28756c5 100644
> > --- a/include/linux/of_fdt.h
> > +++ b/include/linux/of_fdt.h
> > @@ -30,6 +30,8 @@ extern void *of_fdt_get_property(const void *blob,
> >                                int *size);
> >   extern bool of_fdt_is_big_endian(const void *blob,
> >                                unsigned long node);
> > +extern bool of_fdt_device_is_available(const void *blob,
> > +                     unsigned long node);
> >   extern int of_fdt_match(const void *blob, unsigned long node,
> >                       const char *const *compat);
> >   extern void *of_fdt_unflatten_tree(const unsigned long *blob,
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