[PATCHv9 2/2] powerpc/setup: Loosen the mapping between cpu logical id and its seq in dt
Hari Bathini
hbathini at linux.ibm.com
Sun Nov 26 20:30:13 PST 2023
Hi Pingfan, Michael,
On 17/10/23 4:03 pm, Hari Bathini wrote:
>
>
> 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>
>
On second thoughts, probably better off with no impact for
bootcpu < nr_cpu_ids case and changing only two cores logical
numbering otherwise. Something like the below (Please share
your thoughts):
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index ec82f5bda908..78a8312aa8c4 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)
{
@@ -357,6 +359,25 @@ static int __init early_init_dt_scan_cpus(unsigned
long node,
fdt_boot_cpuid_phys(initial_boot_params)) {
found = boot_cpu_count;
found_thread = i;
+ /*
+ * Map boot-cpu logical id into the range
+ * of [0, thread_per_core) if it can't be
+ * accommodated within nr_cpu_ids.
+ */
+ if (i != boot_cpu_count && boot_cpu_count >= nr_cpu_ids) {
+ boot_cpuid = i;
+ DBG("Logical CPU number for boot CPU changed from %d to %d\n",
+ boot_cpu_count, i);
+ } else {
+ boot_cpuid = boot_cpu_count;
+ }
+
+ /* Ensure boot thread is acconted for in nr_cpu_ids */
+ if (boot_cpuid >= nr_cpu_ids) {
+ set_nr_cpu_ids(boot_cpuid + 1);
+ DBG("Adjusted nr_cpu_ids to %u, to include boot CPU.\n",
+ nr_cpu_ids);
+ }
}
#ifdef CONFIG_SMP
/* logical cpu id is always 0 on UP kernels */
@@ -368,9 +389,8 @@ static int __init early_init_dt_scan_cpus(unsigned
long node,
if (found < 0)
return 0;
- DBG("boot cpu: logical %d physical %d\n", found,
+ DBG("boot cpu: logical %d physical %d\n", boot_cpuid,
be32_to_cpu(intserv[found_thread]));
- boot_cpuid = found;
boot_cpu_hwid = be32_to_cpu(intserv[found_thread]);
diff --git a/arch/powerpc/kernel/setup-common.c
b/arch/powerpc/kernel/setup-common.c
index b7b733474b60..f7179525c774 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -409,6 +409,12 @@ static void __init cpu_init_thread_core_maps(int tpc)
u32 *cpu_to_phys_id = NULL;
+struct interrupt_server_node {
+ bool avail;
+ int len;
+ __be32 intserv[];
+};
+
/**
* setup_cpu_maps - initialize the following cpu maps:
* cpu_possible_mask
@@ -429,9 +435,13 @@ u32 *cpu_to_phys_id = NULL;
*/
void __init smp_setup_cpu_maps(void)
{
+ struct interrupt_server_node *core0_node = NULL, *bt_node = NULL;
+ int orig_boot_cpu = -1, orig_boot_thread = -1;
+ bool found_boot_cpu = false;
struct device_node *dn;
- int cpu = 0;
int nthreads = 1;
+ int cpu = 0;
+ int j, len;
DBG("smp_setup_cpu_maps()\n");
@@ -442,9 +452,9 @@ void __init smp_setup_cpu_maps(void)
__func__, nr_cpu_ids * sizeof(u32), __alignof__(u32));
for_each_node_by_type(dn, "cpu") {
+ bool avail, skip = false;
const __be32 *intserv;
__be32 cpu_be;
- int j, len;
DBG(" * %pOF...\n", dn);
@@ -466,29 +476,121 @@ 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");
+
+ for (j = 0; (cpu == 0 || !found_boot_cpu) && j < nthreads; j++) {
+ if (be32_to_cpu(intserv[j]) == boot_cpu_hwid) {
+ found_boot_cpu = true;
+ if (cpu == 0)
+ break;
+
+ /* Original logical CPU number of thread0 in boot core */
+ orig_boot_cpu = cpu;
+ orig_boot_thread = j;
+ bt_node = memblock_alloc(sizeof(struct interrupt_server_node) + len,
+ __alignof__(u32));
+ if (!bt_node)
+ panic("%s: Failed to allocate %zu bytes align=0x%zx\n",
+ __func__,
+ sizeof(struct interrupt_server_node) + len,
+ __alignof__(u32));
+ bt_node->len = len;
+ memcpy(bt_node->intserv, intserv, len);
+ bt_node->avail = avail;
+ skip = true;
+ break;
+ }
+ }
+ /*
+ * Boot CPU not on core0.
+ * Hold off adding core0 until boot core is found as core0
+ * may have to be replaced with boot core if boot core can
+ * not be accommodated within nr_cpu_ids with its original
+ * logical CPU numbering.
+ */
+ if (cpu == 0 && !found_boot_cpu) {
+ core0_node = memblock_alloc(sizeof(struct interrupt_server_node) + len,
+ __alignof__(u32));
+ if (!core0_node)
+ panic("%s: Failed to allocate %zu bytes align=0x%zx\n",
+ __func__,
+ sizeof(struct interrupt_server_node) + len,
+ __alignof__(u32));
+ core0_node->len = len;
+ memcpy(core0_node->intserv, intserv, len);
+ core0_node->avail = avail;
+ skip = true;
+ }
+
+ if (skip) {
+ /* Assumes same number of threads for all cores */
+ cpu += nthreads;
+ continue;
+ }
+
+ for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
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_cpu_possible(cpu, true);
cpu_to_phys_id[cpu] = be32_to_cpu(intserv[j]);
cpu++;
}
- if (cpu >= nr_cpu_ids) {
+ if (found_boot_cpu && cpu >= nr_cpu_ids) {
of_node_put(dn);
break;
}
}
+ /*
+ * Boot CPU not on core0.
+ *
+ * If nr_cpu_ids does not accommodate the original logical CPU
numbering for
+ * boot CPU core, use logical CPU numbers 0 to nthreads for boot CPU core.
+ * Note that boot cpu is already assigned with logical CPU number
somewhere
+ * between 0 to nthreads (depending on the boot thread within the core) in
+ * early_init_dt_scan_cpus() for this case.
+ *
+ * Otherwise, stick with the original logical CPU numbering.
+ */
+ if (bt_node) {
+ int core0_cpu;
+
+ if (orig_boot_cpu + orig_boot_thread >= nr_cpu_ids) {
+ cpu = 0;
+ core0_cpu = orig_boot_cpu;
+ } else {
+ cpu = orig_boot_cpu;
+ core0_cpu = 0;
+ }
+
+ for (j = 0; j < nthreads && core0_cpu < nr_cpu_ids; j++) {
+ DBG(" thread %d -> cpu %d (hard id %d)\n",
+ j, core0_cpu, be32_to_cpu(core0_node->intserv[j]));
+
+ set_cpu_present(core0_cpu, core0_node->avail);
+ set_cpu_possible(core0_cpu, true);
+ cpu_to_phys_id[core0_cpu] = be32_to_cpu(core0_node->intserv[j]);
+ core0_cpu++;
+ }
+
+ for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
+ DBG(" thread %d -> cpu %d (hard id %d)\n",
+ j, cpu, be32_to_cpu(bt_node->intserv[j]));
+
+ set_cpu_present(cpu, bt_node->avail);
+ set_cpu_possible(cpu, true);
+ cpu_to_phys_id[cpu] = be32_to_cpu(bt_node->intserv[j]);
+ cpu++;
+ }
+ }
+
/* If no SMT supported, nthreads is forced to 1 */
if (!cpu_has_feature(CPU_FTR_SMT)) {
DBG(" SMT disabled ! nthreads forced to 1\n");
More information about the kexec
mailing list