* [PATCH] x86/smp: Enforce limit of 512 cpus with MAXSMP and no CPUMASK_OFFSTACK
@ 2019-10-12 7:00 Scott Wood
2019-10-17 16:16 ` [tip: x86/cpu] x86/Kconfig: Enforce limit of 512 CPUs " tip-bot2 for Scott Wood
0 siblings, 1 reply; 2+ messages in thread
From: Scott Wood @ 2019-10-12 7:00 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, H. Peter Anvin
Cc: Mike Travis, x86, linux-kernel, Scott Wood
The help text of NR_CPUS says that the maximum number of cpus supported
without CPUMASK_OFFSTACK is 512. However, NR_CPUS_RANGE_END allows this
limit to be bypassed by MAXSMP even if CPUMASK_OFFSTACK is not set.
This scenario can currently only happen in the RT tree, since it
has "select CPUMASK_OFFSTACK if !PREEMPT_RT_FULL" in MAXSMP. However,
even if we ignore the RT tree, checking for MAXSMP in addition to
CPUMASK_OFFSTACK is redundant.
Signed-off-by: Scott Wood <swood@redhat.com>
---
arch/x86/Kconfig | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d6e1faa28c58..2b526e101dc9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1000,8 +1000,8 @@ config NR_CPUS_RANGE_END
config NR_CPUS_RANGE_END
int
depends on X86_64
- default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
- default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
+ default 8192 if SMP && CPUMASK_OFFSTACK
+ default 512 if SMP && !CPUMASK_OFFSTACK
default 1 if !SMP
config NR_CPUS_DEFAULT
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [tip: x86/cpu] x86/Kconfig: Enforce limit of 512 CPUs with MAXSMP and no CPUMASK_OFFSTACK
2019-10-12 7:00 [PATCH] x86/smp: Enforce limit of 512 cpus with MAXSMP and no CPUMASK_OFFSTACK Scott Wood
@ 2019-10-17 16:16 ` tip-bot2 for Scott Wood
0 siblings, 0 replies; 2+ messages in thread
From: tip-bot2 for Scott Wood @ 2019-10-17 16:16 UTC (permalink / raw)
To: linux-tip-commits
Cc: Scott Wood, Borislav Petkov, H. Peter Anvin, Ingo Molnar,
Mike Travis, Thomas Gleixner, x86-ml, Ingo Molnar,
Borislav Petkov, linux-kernel
The following commit has been merged into the x86/cpu branch of tip:
Commit-ID: 1edae1ae62589f28d00da186465a003e2a7f9c6c
Gitweb: https://git.kernel.org/tip/1edae1ae62589f28d00da186465a003e2a7f9c6c
Author: Scott Wood <swood@redhat.com>
AuthorDate: Sat, 12 Oct 2019 02:00:54 -05:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Thu, 17 Oct 2019 18:04:51 +02:00
x86/Kconfig: Enforce limit of 512 CPUs with MAXSMP and no CPUMASK_OFFSTACK
The help text of NR_CPUS says that the maximum number of CPUs supported
without CPUMASK_OFFSTACK is 512. However, NR_CPUS_RANGE_END allows this
limit to be bypassed by MAXSMP even if CPUMASK_OFFSTACK is not set.
This scenario can currently only happen in the RT tree, since it has
"select CPUMASK_OFFSTACK if !PREEMPT_RT_FULL" in MAXSMP. However,
even if we ignore the RT tree, checking for MAXSMP in addition to
CPUMASK_OFFSTACK is redundant.
Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mike Travis <mike.travis@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191012070054.28657-1-swood@redhat.com
---
arch/x86/Kconfig | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 91c22ee..896f840 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1000,8 +1000,8 @@ config NR_CPUS_RANGE_END
config NR_CPUS_RANGE_END
int
depends on X86_64
- default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
- default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
+ default 8192 if SMP && CPUMASK_OFFSTACK
+ default 512 if SMP && !CPUMASK_OFFSTACK
default 1 if !SMP
config NR_CPUS_DEFAULT
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2019-10-12 7:00 [PATCH] x86/smp: Enforce limit of 512 cpus with MAXSMP and no CPUMASK_OFFSTACK Scott Wood
2019-10-17 16:16 ` [tip: x86/cpu] x86/Kconfig: Enforce limit of 512 CPUs " tip-bot2 for Scott Wood
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