[PATCH v6 (proposal)] powerpc/cpu: enable nr_cpus for crash kernel
Pingfan Liu
kernelfans at gmail.com
Tue May 22 18:23:44 AEST 2018
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
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,
--
2.7.4
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