Re: [PATCHv7 2/4] powerpc/setup: Loosen the mapping between cpu logical id and its seq in dt

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 28/09/2023 à 22:36, Wen Xiong a écrit :
> Hi Pingfan,
> 
> +               avail = intserv_node->avail;
> +               nthreads = intserv_node->len / sizeof(int);
> +               for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
>                          set_cpu_present(cpu, avail);
>                          set_cpu_possible(cpu, true);
> -                       cpu_to_phys_id[cpu] = be32_to_cpu(intserv[j]);
> +                       cpu_to_phys_id[cpu] = be32_to_cpu(intserv_node->intserv[j]);
> +                       DBG("    thread %d -> cpu %d (hard id %d)\n",
> +                           j, cpu, be32_to_cpu(intserv[j]));
> 
> Intserv is not defined. Should "be32_to_cpu(intserv_node->intserv[j])?
>                          cpu++;
>                  }
> +       }

Please don't top-post , see 
https://docs.kernel.org/process/submitting-patches.html#use-trimmed-interleaved-replies-in-email-discussions

Make comments inside the patch directly, making sure that your mail 
client is properly configured to add the standard > in front of all 
lines of the quoted mail.

Christophe

> 
> -----Original Message-----
> From: Pingfan Liu <piliu@redhat.com>
> Sent: Monday, September 25, 2023 2:54 AM
> To: linuxppc-dev@lists.ozlabs.org
> Cc: Pingfan Liu <piliu@redhat.com>; Michael Ellerman <mpe@ellerman.id.au>; Nicholas Piggin <npiggin@gmail.com>; Christophe Leroy <christophe.leroy@csgroup.eu>; Mahesh Salgaonkar <mahesh@linux.ibm.com>; Wen Xiong <wenxiong@us.ibm.com>; Baoquan He <bhe@redhat.com>; Ming Lei <ming.lei@redhat.com>; kexec@lists.infradead.org
> Subject: [EXTERNAL] [PATCHv7 2/4] powerpc/setup: Loosen the mapping between cpu logical id and its seq in dt
> 
> *** Idea ***
> For kexec -p, the boot cpu can be not the cpu0, this causes the problem of allocating memory for paca_ptrs[]. However, in theory, there is no requirement to assign cpu's logical id as its present sequence in the device tree. But there is something like cpu_first_thread_sibling(), which makes assumption on the mapping inside a core. Hence partially loosening the mapping, i.e. unbind the mapping of core while keep the mapping inside a core.
> 
> *** Implement ***
> At this early stage, there are plenty of memory to utilize. Hence, this patch allocates interim memory to link the cpu info on a list, then reorder cpus by changing the list head. As a result, there is a rotate shift between the sequence number in dt and the cpu logical number.
> 
> *** Result ***
> After this patch, a boot-cpu's logical id will always be mapped into the range [0,threads_per_core).
> 
> Besides this, at this phase, all threads in the boot core are forced to be onlined. This restriction will be lifted in a later patch with extra effort.
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Cc: Wen Xiong <wenxiong@us.ibm.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: kexec@lists.infradead.org
> To: linuxppc-dev@lists.ozlabs.org
> ---
>   arch/powerpc/kernel/prom.c         | 25 +++++----
>   arch/powerpc/kernel/setup-common.c | 87 +++++++++++++++++++++++-------
>   2 files changed, 85 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c index ec82f5bda908..87272a2d8c10 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -76,7 +76,9 @@ u64 ppc64_rma_size;
>   unsigned int boot_cpu_node_count __ro_after_init;  #endif  static phys_addr_t first_memblock_size;
> +#ifdef CONFIG_SMP
>   static int __initdata boot_cpu_count;
> +#endif
> 
>   static int __init early_parse_mem(char *p)  { @@ -331,8 +333,7 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>          const __be32 *intserv;
>          int i, nthreads;
>          int len;
> -       int found = -1;
> -       int found_thread = 0;
> +       bool found = false;
> 
>          /* We are scanning "cpu" nodes only */
>          if (type == NULL || strcmp(type, "cpu") != 0) @@ -355,8 +356,15 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>          for (i = 0; i < nthreads; i++) {
>                  if (be32_to_cpu(intserv[i]) ==
>                          fdt_boot_cpuid_phys(initial_boot_params)) {
> -                       found = boot_cpu_count;
> -                       found_thread = i;
> +                       /*
> +                        * always map the boot-cpu logical id into the
> +                        * range of [0, thread_per_core)
> +                        */
> +                       boot_cpuid = i;
> +                       found = true;
> +                       /* This works around the hole in paca_ptrs[]. */
> +                       if (nr_cpu_ids < nthreads)
> +                               set_nr_cpu_ids(nthreads);
>                  }
>   #ifdef CONFIG_SMP
>                  /* logical cpu id is always 0 on UP kernels */ @@ -365,14 +373,13 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>          }
> 
>          /* Not the boot CPU */
> -       if (found < 0)
> +       if (!found)
>                  return 0;
> 
> -       DBG("boot cpu: logical %d physical %d\n", found,
> -           be32_to_cpu(intserv[found_thread]));
> -       boot_cpuid = found;
> +       DBG("boot cpu: logical %d physical %d\n", boot_cpuid,
> +           be32_to_cpu(intserv[boot_cpuid]));
> 
> -       boot_cpu_hwid = be32_to_cpu(intserv[found_thread]);
> +       boot_cpu_hwid = be32_to_cpu(intserv[boot_cpuid]);
> 
>          /*
>           * PAPR defines "logical" PVR values for cpus that diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
> index 1b19a9815672..f6d32324b5a5 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -36,6 +36,7 @@
>   #include <linux/of_platform.h>
>   #include <linux/hugetlb.h>
>   #include <linux/pgtable.h>
> +#include <linux/list.h>
>   #include <asm/io.h>
>   #include <asm/paca.h>
>   #include <asm/processor.h>
> @@ -425,6 +426,13 @@ static void __init cpu_init_thread_core_maps(int tpc)
> 
>   u32 *cpu_to_phys_id = NULL;
> 
> +struct interrupt_server_node {
> +       struct list_head node;
> +       bool    avail;
> +       int     len;
> +       __be32 *intserv;
> +};
> +
>   /**
>    * setup_cpu_maps - initialize the following cpu maps:
>    *                  cpu_possible_mask
> @@ -446,11 +454,16 @@ u32 *cpu_to_phys_id = NULL;  void __init smp_setup_cpu_maps(void)  {
>          struct device_node *dn;
> -       int cpu = 0;
> -       int nthreads = 1;
> +       int shift = 0, cpu = 0;
> +       int j, nthreads = 1;
> +       int len;
> +       struct interrupt_server_node *intserv_node, *n;
> +       struct list_head *bt_node, head;
> +       bool avail, found_boot_cpu = false;
> 
>          DBG("smp_setup_cpu_maps()\n");
> 
> +       INIT_LIST_HEAD(&head);
>          cpu_to_phys_id = memblock_alloc(nr_cpu_ids * sizeof(u32),
>                                          __alignof__(u32));
>          if (!cpu_to_phys_id)
> @@ -460,7 +473,6 @@ void __init smp_setup_cpu_maps(void)
>          for_each_node_by_type(dn, "cpu") {
>                  const __be32 *intserv;
>                  __be32 cpu_be;
> -               int j, len;
> 
>                  DBG("  * %pOF...\n", dn);
> 
> @@ -480,29 +492,68 @@ void __init smp_setup_cpu_maps(void)
>                          }
>                  }
> 
> -               nthreads = len / sizeof(int);
> -
> -               for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
> -                       bool avail;
> +               avail = of_device_is_available(dn);
> +               if (!avail)
> +                       avail = !of_property_match_string(dn,
> +                                       "enable-method", "spin-table");
> 
> -                       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");
> +               intserv_node = memblock_alloc(sizeof(struct interrupt_server_node) + len,
> +                                       __alignof__(u32));
> +               if (!intserv_node)
> +                       panic("%s: Failed to allocate %zu bytes align=0x%zx\n",
> +                               __func__,
> +                               sizeof(struct interrupt_server_node) + len,
> +                               __alignof__(u32));
> +               intserv_node->intserv = (__be32 *)((char *)intserv_node +
> +                                               sizeof(struct interrupt_server_node));
> +               intserv_node->len = len;
> +               memcpy(intserv_node->intserv, intserv, len);
> +               intserv_node->avail = avail;
> +               INIT_LIST_HEAD(&intserv_node->node);
> +               list_add_tail(&intserv_node->node, &head);
> +
> +               if (!found_boot_cpu) {
> +                       nthreads = len / sizeof(int);
> +                       for (j = 0 ; j < nthreads; j++) {
> +                               if (be32_to_cpu(intserv[j]) == boot_cpu_hwid) {
> +                                       bt_node = &intserv_node->node;
> +                                       found_boot_cpu = true;
> +                                       /*
> +                                        * Record the round-shift between dt
> +                                        * seq and cpu logical number
> +                                        */
> +                                       shift = cpu - j;
> +                                       break;
> +                               }
> +
> +                               cpu++;
> +                       }
> +               }
> 
> +       }
> +       cpu = 0;
> +       list_del_init(&head);
> +       /* Select the primary thread, the boot cpu's slibing, as the logic 0 */
> +       list_add_tail(&head, bt_node);
> +       pr_info("the round shift between dt seq and the cpu logic number: %d\n", shift);
> +       list_for_each_entry(intserv_node, &head, node) {
> +
> +               avail = intserv_node->avail;
> +               nthreads = intserv_node->len / sizeof(int);
> +               for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
>                          set_cpu_present(cpu, avail);
>                          set_cpu_possible(cpu, true);
> -                       cpu_to_phys_id[cpu] = be32_to_cpu(intserv[j]);
> +                       cpu_to_phys_id[cpu] = be32_to_cpu(intserv_node->intserv[j]);
> +                       DBG("    thread %d -> cpu %d (hard id %d)\n",
> +                           j, cpu, be32_to_cpu(intserv[j]));
>                          cpu++;
>                  }
> +       }
> 
> -               if (cpu >= nr_cpu_ids) {
> -                       of_node_put(dn);
> -                       break;
> -               }
> +       list_for_each_entry_safe(intserv_node, n, &head, node) {
> +               len = sizeof(struct interrupt_server_node) + intserv_node->len;
> +               memblock_free(intserv_node, len);
>          }
> 
>          /* If no SMT supported, nthreads is forced to 1 */
> --
> 2.31.1
>