[PATCH V3 7/7] riscv: Add config of thread stack size

[guoren at kernel.org]

From: Guo Ren <guoren at linux.alibaba.com>

0cac21b02ba5 ("risc v: use 16KB kernel stack on 64-bit") increase the
thread size mandatory, but some scenarios, such as D1 with a small
memory footprint, would suffer from that. After independent irq stack
support, let's give users a choice to determine their custom stack size.

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
Cc: Andreas Schwab <schwab at suse.de>
---
 arch/riscv/Kconfig                   | 9 +++++++++
 arch/riscv/include/asm/thread_info.h | 4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index da548ed7d107..e436b5793ab6 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -442,6 +442,15 @@ config IRQ_STACKS
 	  Add independent irq & softirq stacks for percpu to prevent kernel stack
 	  overflows. We may save some memory footprint by disabling IRQ_STACKS.
 
+config THREAD_SIZE_ORDER
+	int "Pages of thread stack size (as a power of 2)"
+	range 1 4
+	default "1" if 32BIT
+	default "2" if 64BIT
+	help
+	  Specify the Pages of thread stack size (from 8KB to 64KB), which also
+	  affects irq stack size, which is equal to thread stack size.
+
 endmenu # "Platform type"
 
 menu "Kernel features"
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 043da8ccc7e6..c64d995df6e1 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -19,9 +19,9 @@
 
 /* thread information allocation */
 #ifdef CONFIG_64BIT
-#define THREAD_SIZE_ORDER	(2 + KASAN_STACK_ORDER)
+#define THREAD_SIZE_ORDER	(CONFIG_THREAD_SIZE_ORDER + KASAN_STACK_ORDER)
 #else
-#define THREAD_SIZE_ORDER	(1 + KASAN_STACK_ORDER)
+#define THREAD_SIZE_ORDER	(CONFIG_THREAD_SIZE_ORDER + KASAN_STACK_ORDER)
 #endif
 #define THREAD_SIZE		(PAGE_SIZE << THREAD_SIZE_ORDER)
 
-- 
2.36.1