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[PATCH] kconfig: adjust NR_CPUS defaults
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 14 Jan 2026 12:33:14 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- Delivery-date: Wed, 14 Jan 2026 11:33:23 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Discussion of a RISC-V change revealed that for PPC and RISC-V we don't
really set any default, but rather rely on internals of kconfig picking
the lowest of the permitted values in such a case. Let's make this
explicit, requiring architectures that mean to permit SMP by default to
explicitly record some sensible value here.
Leverage the adjustment to the "1" case to simplify all subsequent ones.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
For not-yet-SMP-capable ports we might go even further and use
range 1 1 if !X86 && (!ARM || MPU)
at the top. Thoughts? (I've not done this right away as it is liable to
get unwieldy when we have a larger number of SMP-capable ports.)
--- a/xen/arch/Kconfig
+++ b/xen/arch/Kconfig
@@ -9,11 +9,11 @@ config NR_CPUS
range 1 1 if ARM && MPU
range 1 16383
default "256" if X86
- default "1" if ARM && MPU
- default "8" if ARM && RCAR3
- default "4" if ARM && QEMU
- default "4" if ARM && MPSOC
- default "128" if ARM
+ default "1" if !ARM || MPU
+ default "8" if RCAR3
+ default "4" if QEMU
+ default "4" if MPSOC
+ default "128"
help
Controls the build-time size of various arrays and bitmaps
associated with multiple-cpu management. It is the upper bound of
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