[PATCHv4,1/3] powerpc, cpu: partially unbind the mapping between cpu logical id and its seq in dt
diff mbox series

Message ID 1520829790-14029-2-git-send-email-kernelfans@gmail.com
State Superseded
Headers show
Series
  • enable nr_cpus for powerpc
Related show

Commit Message

Pingfan Liu March 12, 2018, 4:43 a.m. UTC
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, boot-cpu
will always be mapped into the range [0,threads_per_core).

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
---
 arch/powerpc/include/asm/smp.h     |  1 +
 arch/powerpc/kernel/prom.c         | 25 ++++++++++++++-----------
 arch/powerpc/kernel/setup-common.c | 21 +++++++++++++++++++++
 3 files changed, 36 insertions(+), 11 deletions(-)

Comments

Benjamin Herrenschmidt March 13, 2018, 2:58 a.m. UTC | #1
On Mon, 2018-03-12 at 12:43 +0800, Pingfan Liu wrote:
> 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, boot-cpu
> will always be mapped into the range [0,threads_per_core).

I'm ok with the idea but not fan of the implementation:

> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> ---
>  arch/powerpc/include/asm/smp.h     |  1 +
>  arch/powerpc/kernel/prom.c         | 25 ++++++++++++++-----------
>  arch/powerpc/kernel/setup-common.c | 21 +++++++++++++++++++++
>  3 files changed, 36 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
> index fac963e..1299100 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 boot_cpuhwid;
>  extern int spinning_secondaries;
>  
>  extern void cpu_die(void);
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index da67606..d0ebb25 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -315,8 +315,7 @@ 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)
> @@ -341,8 +340,11 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>  		if (fdt_version(initial_boot_params) >= 2) {
>  			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
> +				 * the range of [0, thread_per_core)
> +				 */
> +				boot_cpuid = i;
> +				found = true;
>  			}

Call it boot_thread_id

>  		} else {
>  			/*
> @@ -351,8 +353,10 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>  			 * off secondary threads.
>  			 */
>  			if (of_get_flat_dt_prop(node,
> -					"linux,boot-cpu", NULL) != NULL)
> -				found = boot_cpu_count;
> +					"linux,boot-cpu", NULL) != NULL) {
> +				boot_cpuid = i;
> +				found = true;
> +			}
>  		}
>  #ifdef CONFIG_SMP
>  		/* logical cpu id is always 0 on UP kernels */
> @@ -361,13 +365,12 @@ 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;
> -	set_hard_smp_processor_id(found, be32_to_cpu(intserv[found_thread]));
> +	boot_cpuhwid = be32_to_cpu(intserv[boot_cpuid]);
> +	DBG("boot cpu: logical %d physical %d\n", boot_cpuid, boot_cpuhwid);
> +	set_hard_smp_processor_id(boot_cpuid, boot_cpuhwid);
>  
>  	/*
>  	 * 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 66f7cc6..1a67344 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -86,6 +86,7 @@ struct machdep_calls *machine_id;
>  EXPORT_SYMBOL(machine_id);
>  
>  int boot_cpuid = -1;
> +int boot_cpuhwid = -1;
>  EXPORT_SYMBOL_GPL(boot_cpuid);
>  
>  /*
> @@ -459,11 +460,17 @@ static void __init cpu_init_thread_core_maps(int tpc)
>  void __init smp_setup_cpu_maps(void)
>  {
>  	struct device_node *dn;
> +	struct device_node *boot_dn = NULL;
> +	bool handling_bootdn = true;
>  	int cpu = 0;
>  	int nthreads = 1;
>  
>  	DBG("smp_setup_cpu_maps()\n");
>  
> +again:
> +	/* E.g. kexec will not boot from the 1st core. So firstly loop to find out
> +	 * the dn of boot-cpu, and map them onto [0, nthreads)
> +	 */
>  	for_each_node_by_type(dn, "cpu") {
>  		const __be32 *intserv;
>  		__be32 cpu_be;
> @@ -488,6 +495,16 @@ void __init smp_setup_cpu_maps(void)
>  
>  		nthreads = len / sizeof(int);
>  
> +		if (handling_bootdn) {
> +			if (boot_cpuid < nthreads &&
> +				be32_to_cpu(intserv[boot_cpuid]) == boot_cpuhwid) {
> +				boot_dn = dn;
> +			}
> +			if (boot_dn == NULL)
> +				continue;
> +		} else if (dn == boot_dn)
> +			continue;
> +
>  		for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
>  			bool avail;
>  
> @@ -509,6 +526,10 @@ void __init smp_setup_cpu_maps(void)
>  			of_node_put(dn);
>  			break;
>  		}
> +		if (handling_bootdn) {
> +			handling_bootdn = false;
> +			goto again;
> +		}
>  	}

You don't need that "again" loop and "handling_bootdn" weird boolean.

Instead, start with cpu = 1 instead of cpu = 0, and rename it to
"next_cpu".

Then, before the thread loop, check if we are on the same core
as boot_cpuhwid:

	if (same_core_as_boot_cpu(intserv)) {
		cpu = 0;
	} else if (next_cpu < nr_cpus_ids) {
		cpu = next_cpu++;
	} else {
		of_node_put(dn);
		break;
	}

>  
>  	/* If no SMT supported, nthreads is forced to 1 */
kernel test robot March 13, 2018, 5:06 a.m. UTC | #2
Hi Pingfan,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v4.16-rc4]
[also build test ERROR on next-20180309]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Pingfan-Liu/powerpc-cpu-partially-unbind-the-mapping-between-cpu-logical-id-and-its-seq-in-dt/20180313-034420
config: powerpc-pq2fads_defconfig (attached as .config)
compiler: powerpc-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=powerpc 

All errors (new ones prefixed by >>):

>> arch/powerpc/kernel/prom.c:79:23: error: 'boot_cpu_count' defined but not used [-Werror=unused-variable]
    static int __initdata boot_cpu_count;
                          ^~~~~~~~~~~~~~
   cc1: all warnings being treated as errors

vim +/boot_cpu_count +79 arch/powerpc/kernel/prom.c

9b6b563c Paul Mackerras         2005-10-06  71  
9b6b563c Paul Mackerras         2005-10-06  72  #ifdef CONFIG_PPC64
28897731 Olof Johansson         2006-04-12  73  int __initdata iommu_is_off;
9b6b563c Paul Mackerras         2005-10-06  74  int __initdata iommu_force_on;
cf00a8d1 Paul Mackerras         2005-10-31  75  unsigned long tce_alloc_start, tce_alloc_end;
cd3db0c4 Benjamin Herrenschmidt 2010-07-06  76  u64 ppc64_rma_size;
9b6b563c Paul Mackerras         2005-10-06  77  #endif
03bf469a Benjamin Herrenschmidt 2011-05-11  78  static phys_addr_t first_memblock_size;
7ac87abb Matt Evans             2011-05-25 @79  static int __initdata boot_cpu_count;
9b6b563c Paul Mackerras         2005-10-06  80  

:::::: The code at line 79 was first introduced by commit
:::::: 7ac87abb8166b99584149fcfb2efef5773a078e9 powerpc: Fix early boot accounting of CPUs

:::::: TO: Matt Evans <matt@ozlabs.org>
:::::: CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Pingfan Liu March 14, 2018, 2:02 a.m. UTC | #3
On Tue, Mar 13, 2018 at 10:58 AM, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> On Mon, 2018-03-12 at 12:43 +0800, Pingfan Liu wrote:
>> 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, boot-cpu
>> will always be mapped into the range [0,threads_per_core).
>
> I'm ok with the idea but not fan of the implementation:
>
>> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
>> ---
>>  arch/powerpc/include/asm/smp.h     |  1 +
>>  arch/powerpc/kernel/prom.c         | 25 ++++++++++++++-----------
>>  arch/powerpc/kernel/setup-common.c | 21 +++++++++++++++++++++
>>  3 files changed, 36 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
>> index fac963e..1299100 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 boot_cpuhwid;
>>  extern int spinning_secondaries;
>>
>>  extern void cpu_die(void);
>> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
>> index da67606..d0ebb25 100644
>> --- a/arch/powerpc/kernel/prom.c
>> +++ b/arch/powerpc/kernel/prom.c
>> @@ -315,8 +315,7 @@ 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)
>> @@ -341,8 +340,11 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>>               if (fdt_version(initial_boot_params) >= 2) {
>>                       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
>> +                              * the range of [0, thread_per_core)
>> +                              */
>> +                             boot_cpuid = i;
>> +                             found = true;
>>                       }
>
> Call it boot_thread_id
>
But I think boot_cpuid has the meaning of global index, while the
thread_id has the meaning of index in a core.

>>               } else {
>>                       /*
>> @@ -351,8 +353,10 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>>                        * off secondary threads.
>>                        */
>>                       if (of_get_flat_dt_prop(node,
>> -                                     "linux,boot-cpu", NULL) != NULL)
>> -                             found = boot_cpu_count;
>> +                                     "linux,boot-cpu", NULL) != NULL) {
>> +                             boot_cpuid = i;
>> +                             found = true;
>> +                     }
>>               }
>>  #ifdef CONFIG_SMP
>>               /* logical cpu id is always 0 on UP kernels */
>> @@ -361,13 +365,12 @@ 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;
>> -     set_hard_smp_processor_id(found, be32_to_cpu(intserv[found_thread]));
>> +     boot_cpuhwid = be32_to_cpu(intserv[boot_cpuid]);
>> +     DBG("boot cpu: logical %d physical %d\n", boot_cpuid, boot_cpuhwid);
>> +     set_hard_smp_processor_id(boot_cpuid, boot_cpuhwid);
>>
>>       /*
>>        * 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 66f7cc6..1a67344 100644
>> --- a/arch/powerpc/kernel/setup-common.c
>> +++ b/arch/powerpc/kernel/setup-common.c
>> @@ -86,6 +86,7 @@ struct machdep_calls *machine_id;
>>  EXPORT_SYMBOL(machine_id);
>>
>>  int boot_cpuid = -1;
>> +int boot_cpuhwid = -1;
>>  EXPORT_SYMBOL_GPL(boot_cpuid);
>>
>>  /*
>> @@ -459,11 +460,17 @@ static void __init cpu_init_thread_core_maps(int tpc)
>>  void __init smp_setup_cpu_maps(void)
>>  {
>>       struct device_node *dn;
>> +     struct device_node *boot_dn = NULL;
>> +     bool handling_bootdn = true;
>>       int cpu = 0;
>>       int nthreads = 1;
>>
>>       DBG("smp_setup_cpu_maps()\n");
>>
>> +again:
>> +     /* E.g. kexec will not boot from the 1st core. So firstly loop to find out
>> +      * the dn of boot-cpu, and map them onto [0, nthreads)
>> +      */
>>       for_each_node_by_type(dn, "cpu") {
>>               const __be32 *intserv;
>>               __be32 cpu_be;
>> @@ -488,6 +495,16 @@ void __init smp_setup_cpu_maps(void)
>>
>>               nthreads = len / sizeof(int);
>>
>> +             if (handling_bootdn) {
>> +                     if (boot_cpuid < nthreads &&
>> +                             be32_to_cpu(intserv[boot_cpuid]) == boot_cpuhwid) {
>> +                             boot_dn = dn;
>> +                     }
>> +                     if (boot_dn == NULL)
>> +                             continue;
>> +             } else if (dn == boot_dn)
>> +                     continue;
>> +
>>               for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
>>                       bool avail;
>>
>> @@ -509,6 +526,10 @@ void __init smp_setup_cpu_maps(void)
>>                       of_node_put(dn);
>>                       break;
>>               }
>> +             if (handling_bootdn) {
>> +                     handling_bootdn = false;
>> +                     goto again;
>> +             }
>>       }
>
> You don't need that "again" loop and "handling_bootdn" weird boolean.
>
> Instead, start with cpu = 1 instead of cpu = 0, and rename it to
> "next_cpu".
>
> Then, before the thread loop, check if we are on the same core
> as boot_cpuhwid:
>
>         if (same_core_as_boot_cpu(intserv)) {
>                 cpu = 0;
>         } else if (next_cpu < nr_cpus_ids) {
>                 cpu = next_cpu++;
>         } else {
>                 of_node_put(dn);
>                 break;
>         }
>
OK.


Thanks for your review.

Regards,
Pingfan

Patch
diff mbox series

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index fac963e..1299100 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 boot_cpuhwid;
 extern int spinning_secondaries;
 
 extern void cpu_die(void);
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index da67606..d0ebb25 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -315,8 +315,7 @@  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)
@@ -341,8 +340,11 @@  static int __init early_init_dt_scan_cpus(unsigned long node,
 		if (fdt_version(initial_boot_params) >= 2) {
 			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
+				 * the range of [0, thread_per_core)
+				 */
+				boot_cpuid = i;
+				found = true;
 			}
 		} else {
 			/*
@@ -351,8 +353,10 @@  static int __init early_init_dt_scan_cpus(unsigned long node,
 			 * off secondary threads.
 			 */
 			if (of_get_flat_dt_prop(node,
-					"linux,boot-cpu", NULL) != NULL)
-				found = boot_cpu_count;
+					"linux,boot-cpu", NULL) != NULL) {
+				boot_cpuid = i;
+				found = true;
+			}
 		}
 #ifdef CONFIG_SMP
 		/* logical cpu id is always 0 on UP kernels */
@@ -361,13 +365,12 @@  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;
-	set_hard_smp_processor_id(found, be32_to_cpu(intserv[found_thread]));
+	boot_cpuhwid = be32_to_cpu(intserv[boot_cpuid]);
+	DBG("boot cpu: logical %d physical %d\n", boot_cpuid, boot_cpuhwid);
+	set_hard_smp_processor_id(boot_cpuid, boot_cpuhwid);
 
 	/*
 	 * 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 66f7cc6..1a67344 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -86,6 +86,7 @@  struct machdep_calls *machine_id;
 EXPORT_SYMBOL(machine_id);
 
 int boot_cpuid = -1;
+int boot_cpuhwid = -1;
 EXPORT_SYMBOL_GPL(boot_cpuid);
 
 /*
@@ -459,11 +460,17 @@  static void __init cpu_init_thread_core_maps(int tpc)
 void __init smp_setup_cpu_maps(void)
 {
 	struct device_node *dn;
+	struct device_node *boot_dn = NULL;
+	bool handling_bootdn = true;
 	int cpu = 0;
 	int nthreads = 1;
 
 	DBG("smp_setup_cpu_maps()\n");
 
+again:
+	/* E.g. kexec will not boot from the 1st core. So firstly loop to find out
+	 * the dn of boot-cpu, and map them onto [0, nthreads)
+	 */
 	for_each_node_by_type(dn, "cpu") {
 		const __be32 *intserv;
 		__be32 cpu_be;
@@ -488,6 +495,16 @@  void __init smp_setup_cpu_maps(void)
 
 		nthreads = len / sizeof(int);
 
+		if (handling_bootdn) {
+			if (boot_cpuid < nthreads &&
+				be32_to_cpu(intserv[boot_cpuid]) == boot_cpuhwid) {
+				boot_dn = dn;
+			}
+			if (boot_dn == NULL)
+				continue;
+		} else if (dn == boot_dn)
+			continue;
+
 		for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
 			bool avail;
 
@@ -509,6 +526,10 @@  void __init smp_setup_cpu_maps(void)
 			of_node_put(dn);
 			break;
 		}
+		if (handling_bootdn) {
+			handling_bootdn = false;
+			goto again;
+		}
 	}
 
 	/* If no SMT supported, nthreads is forced to 1 */