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Subject[PATCH v3] RISC-V: Increase range and default value of NR_CPUS
Date
Currently, the range and default value of NR_CPUS is too restrictive
for high-end RISC-V systems with large number of HARTs. The latest
QEMU virt machine supports upto 512 CPUs so the current NR_CPUS is
restrictive for QEMU as well. Other major architectures (such as
ARM64, x86_64, MIPS, etc) have a much higher range and default
value of NR_CPUS.

This patch increases NR_CPUS range to 2-512 and default value to
XLEN (i.e. 32 for RV32 and 64 for RV64).

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
Changes since v2:
- Rebased on Linux-5.18-rc3
- Use a different range when SBI v0.1 is enabled
Changes since v1:
- Updated NR_CPUS range to 2-512 which reflects maximum number of
CPUs supported by QEMU virt machine.
---
arch/riscv/Kconfig | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 00fd9c548f26..1823f281069f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -275,10 +275,13 @@ config SMP
If you don't know what to do here, say N.

config NR_CPUS
- int "Maximum number of CPUs (2-32)"
- range 2 32
+ int "Maximum number of CPUs (2-512)"
depends on SMP
- default "8"
+ range 2 512 if !SBI_V01
+ range 2 32 if SBI_V01 && 32BIT
+ range 2 64 if SBI_V01 && 64BIT
+ default "32" if 32BIT
+ default "64" if 64BIT

config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs"
--
2.25.1
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