* [PATCH] arch/sparc: support NR_CPUS = 4096
@ 2017-06-01 21:39 Jane Chu
2017-06-04 23:46 ` David Miller
0 siblings, 1 reply; 5+ messages in thread
From: Jane Chu @ 2017-06-01 21:39 UTC (permalink / raw)
To: davem, tglx; +Cc: atish.patra, Liam.Howlett, sparclinux, linux-kernel, jane.chu
Linux SPARC64 limits NR_CPUS to 4064 because init_cpu_send_mondo_info()
only allocates a single page for NR_CPUS mondo entries. Thus we cannot
use all 4096 CPUs on some SPARC platforms.
To fix, allocate (2^order) pages where order is set according to the size
of cpu_list for possible cpus. Since cpu_list_pa and cpu_mondo_block_pa
are not used in asm code, there are no imm13 offsets from the base PA
that will break because they can only reach one page.
Orabug: 25505750
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Reviewed-by: Atish Patra <atish.patra@oracle.com>
---
arch/sparc/Kconfig | 4 ++--
arch/sparc/kernel/irq_64.c | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 58243b0..4399be7 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -192,9 +192,9 @@ config NR_CPUS
int "Maximum number of CPUs"
depends on SMP
range 2 32 if SPARC32
- range 2 1024 if SPARC64
+ range 2 4096 if SPARC64
default 32 if SPARC32
- default 64 if SPARC64
+ default 4096 if SPARC64
source kernel/Kconfig.hz
diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index 4d0248a..5b19108 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -1034,12 +1034,12 @@ static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
{
#ifdef CONFIG_SMP
unsigned long page;
+ unsigned int order;
- BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > (PAGE_SIZE - 64));
-
- page = get_zeroed_page(GFP_KERNEL);
+ order = get_order(num_possible_cpus() * sizeof(u16) + 64);
+ page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
if (!page) {
- prom_printf("SUN4V: Error, cannot allocate cpu mondo page.\n");
+ prom_printf("SUN4V: Error, cannot allocate cpu mondo pages.\n");
prom_halt();
}
--
1.7.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] arch/sparc: support NR_CPUS = 4096
2017-06-01 21:39 [PATCH] arch/sparc: support NR_CPUS = 4096 Jane Chu
@ 2017-06-04 23:46 ` David Miller
2017-06-05 19:15 ` jane.chu
2017-06-05 21:32 ` jane.chu
0 siblings, 2 replies; 5+ messages in thread
From: David Miller @ 2017-06-04 23:46 UTC (permalink / raw)
To: jane.chu; +Cc: tglx, atish.patra, Liam.Howlett, sparclinux, linux-kernel
From: Jane Chu <jane.chu@oracle.com>
Date: Thu, 1 Jun 2017 15:39:13 -0600
> diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
> index 4d0248a..5b19108 100644
> --- a/arch/sparc/kernel/irq_64.c
> +++ b/arch/sparc/kernel/irq_64.c
> @@ -1034,12 +1034,12 @@ static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
> {
> #ifdef CONFIG_SMP
> unsigned long page;
> + unsigned int order;
>
> - BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > (PAGE_SIZE - 64));
> -
> - page = get_zeroed_page(GFP_KERNEL);
> + order = get_order(num_possible_cpus() * sizeof(u16) + 64);
> + page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
> if (!page) {
The only reason we allocated these two items together was because it
was convenient and it all fit into a single page.
Since it now doesn't, it makes sense to split it up.
Simply use a single page for the cpu_list_pa and kzalloc for the
cpu_mondo_block.
This also allows to keep the BUILD_BUG_ON(), which I really wish
you hadn't tried to remove.
static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
{
#ifdef CONFIG_SMP
unsigned long page;
void *mondo;
BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > PAGE_SIZE);
mondo = kzalloc(64, GFP_KERNEL);
if (!mondo) {
prom_printf("SUN4V: Error, cannot allocate mondo block.\n");
prom_halt();
}
tb->cpu_mondo_block_pa = __pa(mondo);
page = get_zeroed_page(GFP_KERNEL);
if (!page) {
prom_printf("SUN4V: Error, cannot allocate cpu list page.\n");
prom_halt();
}
tb->cpu_list_pa = __pa(page);
#endif
}
Thanks.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arch/sparc: support NR_CPUS = 4096
2017-06-04 23:46 ` David Miller
@ 2017-06-05 19:15 ` jane.chu
2017-06-05 21:32 ` jane.chu
1 sibling, 0 replies; 5+ messages in thread
From: jane.chu @ 2017-06-05 19:15 UTC (permalink / raw)
To: David Miller
Cc: tglx, atish.patra, Liam.Howlett, sparclinux, linux-kernel, JANE.CHU
Hi, David,
On 06/04/2017 04:46 PM, David Miller wrote:
> From: Jane Chu <jane.chu@oracle.com>
> Date: Thu, 1 Jun 2017 15:39:13 -0600
>
>> diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
>> index 4d0248a..5b19108 100644
>> --- a/arch/sparc/kernel/irq_64.c
>> +++ b/arch/sparc/kernel/irq_64.c
>> @@ -1034,12 +1034,12 @@ static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
>> {
>> #ifdef CONFIG_SMP
>> unsigned long page;
>> + unsigned int order;
>>
>> - BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > (PAGE_SIZE - 64));
>> -
>> - page = get_zeroed_page(GFP_KERNEL);
>> + order = get_order(num_possible_cpus() * sizeof(u16) + 64);
>> + page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
>> if (!page) {
> The only reason we allocated these two items together was because it
> was convenient and it all fit into a single page.
>
> Since it now doesn't, it makes sense to split it up.
>
> Simply use a single page for the cpu_list_pa and kzalloc for the
> cpu_mondo_block.
>
> This also allows to keep the BUILD_BUG_ON(), which I really wish
> you hadn't tried to remove.
Good point! I will just add a comment for future maintenance that
the mondo trap block needs to be 64byte aligned.
>
> static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
> {
> #ifdef CONFIG_SMP
> unsigned long page;
> void *mondo;
>
> BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > PAGE_SIZE);
>
> mondo = kzalloc(64, GFP_KERNEL);
> if (!mondo) {
> prom_printf("SUN4V: Error, cannot allocate mondo block.\n");
> prom_halt();
> }
> tb->cpu_mondo_block_pa = __pa(mondo);
>
> page = get_zeroed_page(GFP_KERNEL);
> if (!page) {
> prom_printf("SUN4V: Error, cannot allocate cpu list page.\n");
> prom_halt();
> }
> tb->cpu_list_pa = __pa(page);
> #endif
> }
Thanks a lot!
-jane
>
> Thanks.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arch/sparc: support NR_CPUS = 4096
2017-06-04 23:46 ` David Miller
2017-06-05 19:15 ` jane.chu
@ 2017-06-05 21:32 ` jane.chu
2017-06-05 21:50 ` David Miller
1 sibling, 1 reply; 5+ messages in thread
From: jane.chu @ 2017-06-05 21:32 UTC (permalink / raw)
To: David Miller
Cc: tglx, atish.patra, Liam.Howlett, sparclinux, linux-kernel,
Steven Sistare
Hi,
I have a question about a checkpatch.pl warning against the
use of NR_CPUS -
$ ./scripts/checkpatch.pl diff.patch
WARNING: usage of NR_CPUS is often wrong - consider using
cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc
#14: FILE: arch/sparc/kernel/irq_64.c:1039:
+ BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > PAGE_SIZE);
num_possible_cpus() is the hard limit on a domain without platform reboot,
it is capped by both NR_CPUS and 'max_cpus' (a platform property in the
machine description). So it is theoretically possible to have NR_CPUS>4096
but num_possible_cpus() < 4096 -- a scenario I think we'd prefer to reject.
Is it okay to ignore the checkpatch.pl warning in this case?
thanks,
-jane
On 06/04/2017 04:46 PM, David Miller wrote:
> From: Jane Chu <jane.chu@oracle.com>
> Date: Thu, 1 Jun 2017 15:39:13 -0600
>
>> diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
>> index 4d0248a..5b19108 100644
>> --- a/arch/sparc/kernel/irq_64.c
>> +++ b/arch/sparc/kernel/irq_64.c
>> @@ -1034,12 +1034,12 @@ static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
>> {
>> #ifdef CONFIG_SMP
>> unsigned long page;
>> + unsigned int order;
>>
>> - BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > (PAGE_SIZE - 64));
>> -
>> - page = get_zeroed_page(GFP_KERNEL);
>> + order = get_order(num_possible_cpus() * sizeof(u16) + 64);
>> + page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
>> if (!page) {
> The only reason we allocated these two items together was because it
> was convenient and it all fit into a single page.
>
> Since it now doesn't, it makes sense to split it up.
>
> Simply use a single page for the cpu_list_pa and kzalloc for the
> cpu_mondo_block.
>
> This also allows to keep the BUILD_BUG_ON(), which I really wish
> you hadn't tried to remove.
>
> static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
> {
> #ifdef CONFIG_SMP
> unsigned long page;
> void *mondo;
>
> BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > PAGE_SIZE);
>
> mondo = kzalloc(64, GFP_KERNEL);
> if (!mondo) {
> prom_printf("SUN4V: Error, cannot allocate mondo block.\n");
> prom_halt();
> }
> tb->cpu_mondo_block_pa = __pa(mondo);
>
> page = get_zeroed_page(GFP_KERNEL);
> if (!page) {
> prom_printf("SUN4V: Error, cannot allocate cpu list page.\n");
> prom_halt();
> }
> tb->cpu_list_pa = __pa(page);
> #endif
> }
>
> Thanks.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arch/sparc: support NR_CPUS = 4096
2017-06-05 21:32 ` jane.chu
@ 2017-06-05 21:50 ` David Miller
0 siblings, 0 replies; 5+ messages in thread
From: David Miller @ 2017-06-05 21:50 UTC (permalink / raw)
To: jane.chu
Cc: tglx, atish.patra, Liam.Howlett, sparclinux, linux-kernel,
steven.sistare
From: jane.chu@oracle.com
Date: Mon, 5 Jun 2017 14:32:10 -0700
> Is it okay to ignore the checkpatch.pl warning in this case?
I absolutely think you can ignore this warning.
Thanks.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-06-05 21:50 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-06-01 21:39 [PATCH] arch/sparc: support NR_CPUS = 4096 Jane Chu
2017-06-04 23:46 ` David Miller
2017-06-05 19:15 ` jane.chu
2017-06-05 21:32 ` jane.chu
2017-06-05 21:50 ` David Miller
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).