riscv: stack: Add config of thread stack size

The commit 0cac21b02ba5 ("riscv: use 16KB kernel stack on 64-bit")
increases 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.

Link: https://lore.kernel.org/linux-riscv/5f6e6c39-b846-4392-b468-02202404de28@www.fastmail.com/
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20230614013018.2168426-4-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f515cb1..0599bba 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -599,6 +599,16 @@ 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 "Kernel stack size (in power-of-two numbers of page size)" if VMAP_STACK && EXPERT
+       range 0 4
+       default 1 if 32BIT && !KASAN
+       default 3 if 64BIT && KASAN
+       default 2
+       help
+         Specify the Pages of thread stack size (from 4KB 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 2f32875..1833beb 100644 (file)
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -11,18 +11,8 @@
 #include <asm/page.h>
 #include <linux/const.h>
 
-#ifdef CONFIG_KASAN
-#define KASAN_STACK_ORDER 1
-#else
-#define KASAN_STACK_ORDER 0
-#endif
-
 /* thread information allocation */
-#ifdef CONFIG_64BIT
-#define THREAD_SIZE_ORDER      (2 + KASAN_STACK_ORDER)
-#else
-#define THREAD_SIZE_ORDER      (1 + KASAN_STACK_ORDER)
-#endif
+#define THREAD_SIZE_ORDER      CONFIG_THREAD_SIZE_ORDER
 #define THREAD_SIZE            (PAGE_SIZE << THREAD_SIZE_ORDER)
 
 /*