On 06/05/2017 05:57 PM, David Miller wrote:
From: Jane Chu <jane....@oracle.com>
Date: Mon, 5 Jun 2017 16:48:31 -0600
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....@oracle.com>
Reviewed-by: Bob Picco <bob.pi...@oracle.com>
Reviewed-by: Atish Patra <atish.pa...@oracle.com>
---
arch/sparc/Kconfig | 4 ++--
arch/sparc/kernel/irq_64.c | 16 ++++++++++++----
2 files changed, 14 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..cc8f6c3 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -1034,17 +1034,25 @@ 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 - 64));
+ BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > PAGE_SIZE);
+
+ /* Make sure mondo block is 64byte aligned */
+ 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);
Hmmm, you said that this has to be 64 byte aligned right? We might have
to do something in order to insure that, as kmalloc() only guarantees
ARCH_KMALLOC_MINALIGN which I think is 8 on sparc.
Yes.
I suppose this would work:
mondo = kzalloc(64 + 63, GFP_KERNEL);
and then 64-byte align that pointer.
On sun4v sparc, it looks like kzalloc(64, GFP_KERNEL) ends up allocating
from kmalloc_caches[6] - a 64-byte kmem-cache allocated by
kmem_cache_init() with SLAB_HWCACHE_ALIGN flag set, so it's in
l3-cache-line-size
alignment, i.e. 64byte. I printed out the 'mondo' pa and verified that.
thanks!
-jane
