[PATCHv9 2/2] powerpc/setup: Loosen the mapping between cpu logical id and its seq in dt
Hari Bathini
hbathini at linux.ibm.com
Tue Oct 17 03:33:54 PDT 2023
On 17/10/23 7:58 am, Pingfan Liu wrote:
> *** 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 at redhat.com>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Nicholas Piggin <npiggin at gmail.com>
> Cc: Christophe Leroy <christophe.leroy at csgroup.eu>
> Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> Cc: Wen Xiong <wenxiong at us.ibm.com>
> Cc: Baoquan He <bhe at redhat.com>
> Cc: Ming Lei <ming.lei at redhat.com>
> Cc: Sourabh Jain <sourabhjain at linux.ibm.com>
> Cc: Hari Bathini <hbathini at linux.ibm.com>
> Cc: kexec at lists.infradead.org
> To: linuxppc-dev at lists.ozlabs.org
Thanks for working on this, Pingfan.
Looks good to me.
Acked-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
> arch/powerpc/kernel/prom.c | 25 +++++----
> arch/powerpc/kernel/setup-common.c | 84 +++++++++++++++++++++++-------
> 2 files changed, 82 insertions(+), 27 deletions(-)
>
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index ec82f5bda908..7ed9034912ca 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 forces all threads in a core to be online */
> + if (nr_cpu_ids % nthreads != 0)
> + set_nr_cpu_ids(ALIGN(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 707f0490639d..9802c7e5ee2f 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -36,6 +36,7 @@
> #include <linux/of_irq.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 +492,65 @@ void __init smp_setup_cpu_maps(void)
> }
> }
>
> - nthreads = len / sizeof(int);
> + avail = of_device_is_available(dn);
> + if (!avail)
> + avail = !of_property_match_string(dn,
> + "enable-method", "spin-table");
>
> - 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");
> + 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->len = len;
> + memcpy(intserv_node->intserv, intserv, len);
> + intserv_node->avail = avail;
> + 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_node->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 */
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