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

Christophe Leroy christophe.leroy at csgroup.eu
Fri Jan 26 06:39:38 AEDT 2024


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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