* [PATCH] LoongArch: Increase COMMAND_LINE_SIZE to 4096
@ 2025-08-12 12:20 Ming Wang
2025-08-17 3:42 ` Huacai Chen
0 siblings, 1 reply; 3+ messages in thread
From: Ming Wang @ 2025-08-12 12:20 UTC (permalink / raw)
To: Huacai Chen, WANG Xuerui, Paul Walmsley, Albert Ou,
Alexandre Ghiti, Ming Wang, loongarch, linux-kernel, linux-riscv
Cc: lixuefeng, chenhuacai, Huang Cun
The default COMMAND_LINE_SIZE of 512, inherited from asm-generic, is
too small for modern use cases. For example, kdump configurations or
extensive debugging parameters can easily exceed this limit.
Therefore, increase the command line size to 4096 bytes, aligning
LoongArch with the MIPS architecture. This change follows a broader
trend among architectures to raise this limit to support modern needs;
for instance, PowerPC increased its value for similar reasons in
commit a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE to 2048").
Similar to the change made for RISC-V in commit 61fc1ee8be26
("riscv: Bump COMMAND_LINE_SIZE value to 1024"), this is considered
a safe change. The broader kernel community has reached a consensus
that modifying COMMAND_LINE_SIZE from UAPI headers does not
constitute a uABI breakage, as well-behaved userspace applications
should not rely on this macro.
Suggested-by: Huang Cun <cunhuang@tencent.com>
Signed-off-by: Ming Wang <wangming01@loongson.cn>
---
arch/loongarch/include/uapi/asm/setup.h | 8 ++++++++
1 file changed, 8 insertions(+)
create mode 100644 arch/loongarch/include/uapi/asm/setup.h
diff --git a/arch/loongarch/include/uapi/asm/setup.h b/arch/loongarch/include/uapi/asm/setup.h
new file mode 100644
index 000000000000..d46363ce3e02
--- /dev/null
+++ b/arch/loongarch/include/uapi/asm/setup.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef _UAPI_ASM_LOONGARCH_SETUP_H
+#define _UAPI_ASM_LOONGARCH_SETUP_H
+
+#define COMMAND_LINE_SIZE 4096
+
+#endif /* _UAPI_ASM_LOONGARCH_SETUP_H */
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] LoongArch: Increase COMMAND_LINE_SIZE to 4096
2025-08-12 12:20 Ming Wang
@ 2025-08-17 3:42 ` Huacai Chen
0 siblings, 0 replies; 3+ messages in thread
From: Huacai Chen @ 2025-08-17 3:42 UTC (permalink / raw)
To: Ming Wang
Cc: WANG Xuerui, Paul Walmsley, Albert Ou, Alexandre Ghiti, loongarch,
linux-kernel, linux-riscv, lixuefeng, chenhuacai, Huang Cun
Applied, thanks.
Huacai
On Tue, Aug 12, 2025 at 8:20 PM Ming Wang <wangming01@loongson.cn> wrote:
>
> The default COMMAND_LINE_SIZE of 512, inherited from asm-generic, is
> too small for modern use cases. For example, kdump configurations or
> extensive debugging parameters can easily exceed this limit.
>
> Therefore, increase the command line size to 4096 bytes, aligning
> LoongArch with the MIPS architecture. This change follows a broader
> trend among architectures to raise this limit to support modern needs;
> for instance, PowerPC increased its value for similar reasons in
> commit a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE to 2048").
>
> Similar to the change made for RISC-V in commit 61fc1ee8be26
> ("riscv: Bump COMMAND_LINE_SIZE value to 1024"), this is considered
> a safe change. The broader kernel community has reached a consensus
> that modifying COMMAND_LINE_SIZE from UAPI headers does not
> constitute a uABI breakage, as well-behaved userspace applications
> should not rely on this macro.
>
> Suggested-by: Huang Cun <cunhuang@tencent.com>
> Signed-off-by: Ming Wang <wangming01@loongson.cn>
> ---
> arch/loongarch/include/uapi/asm/setup.h | 8 ++++++++
> 1 file changed, 8 insertions(+)
> create mode 100644 arch/loongarch/include/uapi/asm/setup.h
>
> diff --git a/arch/loongarch/include/uapi/asm/setup.h b/arch/loongarch/include/uapi/asm/setup.h
> new file mode 100644
> index 000000000000..d46363ce3e02
> --- /dev/null
> +++ b/arch/loongarch/include/uapi/asm/setup.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +
> +#ifndef _UAPI_ASM_LOONGARCH_SETUP_H
> +#define _UAPI_ASM_LOONGARCH_SETUP_H
> +
> +#define COMMAND_LINE_SIZE 4096
> +
> +#endif /* _UAPI_ASM_LOONGARCH_SETUP_H */
> --
> 2.43.0
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] LoongArch: Increase COMMAND_LINE_SIZE to 4096
@ 2025-08-17 7:57 Xose Vazquez Perez
0 siblings, 0 replies; 3+ messages in thread
From: Xose Vazquez Perez @ 2025-08-17 7:57 UTC (permalink / raw)
To: Ming Wang; +Cc: LINUX_ARCH-ML, API-ML, KERNEL-ML, X86-ML
Ming Wang wrote:
> The default COMMAND_LINE_SIZE of 512, inherited from asm-generic, is
> too small for modern use cases. For example, kdump configurations or
> extensive debugging parameters can easily exceed this limit.
>
> Therefore, increase the command line size to 4096 bytes, aligning
> LoongArch with the MIPS architecture. This change follows a broader
> trend among architectures to raise this limit to support modern needs;
> for instance, PowerPC increased its value for similar reasons in
> commit a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE to 2048").
>
> Similar to the change made for RISC-V in commit 61fc1ee8be26
> ("riscv: Bump COMMAND_LINE_SIZE value to 1024"), this is considered
> a safe change. The broader kernel community has reached a consensus
> that modifying COMMAND_LINE_SIZE from UAPI headers does not
> constitute a uABI breakage, as well-behaved userspace applications
> should not rely on this macro.
>
> Suggested-by: Huang Cun <cunhuang@tencent.com>
> Signed-off-by: Ming Wang <wangming01@loongson.cn>
> ---
> arch/loongarch/include/uapi/asm/setup.h | 8 ++++++++
> 1 file changed, 8 insertions(+)
> create mode 100644 arch/loongarch/include/uapi/asm/setup.h
>
> diff --git a/arch/loongarch/include/uapi/asm/setup.h b/arch/loongarch/include/uapi/asm/setup.h
> new file mode 100644
> index 000000000000..d46363ce3e02
> --- /dev/null
> +++ b/arch/loongarch/include/uapi/asm/setup.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +
> +#ifndef _UAPI_ASM_LOONGARCH_SETUP_H
> +#define _UAPI_ASM_LOONGARCH_SETUP_H
> +
> +#define COMMAND_LINE_SIZE 4096
> +
> +#endif /* _UAPI_ASM_LOONGARCH_SETUP_H */
> --
> 2.43.0
A bit chaotic and arbitrary sizes:
$ git grep "define.*COMMAND_LINE_SIZE"
arch/alpha/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 256
arch/arc/include/asm/setup.h:#define COMMAND_LINE_SIZE 256
arch/arm64/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 2048
arch/arm/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 1024
arch/m68k/include/asm/setup.h:#define CL_SIZE COMMAND_LINE_SIZE
arch/m68k/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 256
arch/microblaze/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 256
arch/mips/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 4096
arch/mips/loongson64/reset.c:#define KEXEC_ARGV_SIZE COMMAND_LINE_SIZE
arch/parisc/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 1024
arch/powerpc/boot/ops.h:#define BOOT_COMMAND_LINE_SIZE 2048
arch/powerpc/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 2048
arch/riscv/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 1024
arch/s390/include/asm/setup.h:#define COMMAND_LINE_SIZE CONFIG_COMMAND_LINE_SIZE
arch/s390/include/asm/setup.h:#define LEGACY_COMMAND_LINE_SIZE 896
arch/sparc/include/uapi/asm/setup.h:# define COMMAND_LINE_SIZE 2048
arch/sparc/include/uapi/asm/setup.h:# define COMMAND_LINE_SIZE 256
arch/um/include/asm/setup.h:#define COMMAND_LINE_SIZE 4096
arch/x86/include/asm/setup.h:#define COMMAND_LINE_SIZE 2048
arch/xtensa/include/uapi/asm/setup.h:#define COMMAND_LINE_SIZE 256
include/uapi/asm-generic/setup.h:#define COMMAND_LINE_SIZE 512
kernel/trace/ftrace.c:#define FTRACE_FILTER_SIZE COMMAND_LINE_SIZE
tools/power/x86/turbostat/turbostat.c:#define COMMAND_LINE_SIZE 2048
tools/testing/selftests/kho/init.c:#define COMMAND_LINE_SIZE 2048
Maybe they should be standardized ???
And for s390 it is configurable, see 622021cd6c560
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2025-08-17 3:42 ` Huacai Chen
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