From: Scott Wood <swood@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>
Cc: Mike Travis <mike.travis@hpe.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Scott Wood <swood@redhat.com>
Subject: [PATCH] x86/smp: Enforce limit of 512 cpus with MAXSMP and no CPUMASK_OFFSTACK
Date: Sat, 12 Oct 2019 02:00:54 -0500 [thread overview]
Message-ID: <20191012070054.28657-1-swood@redhat.com> (raw)
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
next reply other threads:[~2019-10-12 7:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-12 7:00 Scott Wood [this message]
2019-10-17 16:16 ` [tip: x86/cpu] x86/Kconfig: Enforce limit of 512 CPUs with MAXSMP and no CPUMASK_OFFSTACK tip-bot2 for Scott Wood
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