Patch "arch/sparc: support NR_CPUS = 4096" has been added to the 4.4-stable tree

Patch "arch/sparc: support NR_CPUS = 4096" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    arch/sparc: support NR_CPUS = 4096

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arch-sparc-support-nr_cpus-4096.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Jun  8 09:20:28 CEST 2017
From: Jane Chu <jane.chu@oracle.com>
Date: Tue, 6 Jun 2017 14:32:29 -0600
Subject: arch/sparc: support NR_CPUS = 4096

From: Jane Chu <jane.chu@oracle.com>


[ Upstream commit c79a13734d104b5b147d7cb0870276ccdd660dae ]

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/sparc/Kconfig         |    4 ++--
 arch/sparc/kernel/irq_64.c |   17 +++++++++++++----
 2 files changed, 15 insertions(+), 6 deletions(-)

--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -182,9 +182,9 @@ 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
 
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -1034,17 +1034,26 @@ static void __init init_cpu_send_mondo_i
 {
 #ifdef CONFIG_SMP
 	unsigned long page;
+	void *mondo, *p;
 
-	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 */
+	p = kzalloc(127, GFP_KERNEL);
+	if (!p) {
+		prom_printf("SUN4V: Error, cannot allocate mondo block.\n");
+		prom_halt();
+	}
+	mondo = (void *)(((unsigned long)p + 63) & ~0x3f);
+	tb->cpu_mondo_block_pa = __pa(mondo);
 
 	page = get_zeroed_page(GFP_KERNEL);
 	if (!page) {
-		prom_printf("SUN4V: Error, cannot allocate cpu mondo page.\n");
+		prom_printf("SUN4V: Error, cannot allocate cpu list page.\n");
 		prom_halt();
 	}
 
-	tb->cpu_mondo_block_pa = __pa(page);
-	tb->cpu_list_pa = __pa(page + 64);
+	tb->cpu_list_pa = __pa(page);
 #endif
 }
 


Patches currently in stable-queue which might be from jane.chu@oracle.com are

queue-4.4/arch-sparc-support-nr_cpus-4096.patch