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[PATCH V2] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg

Huacai Chen posted 1 patch 6 months, 4 weeks ago
There is a newer version of this series
arch/loongarch/include/asm/irqflags.h | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
[PATCH V2] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by Huacai Chen 6 months, 4 weeks ago 
When building kernel with LLVM there are occasionally such errors:

In file included from ./include/linux/spinlock.h:59:
In file included from ./include/linux/irqflags.h:17:
arch/loongarch/include/asm/irqflags.h:38:3: error: must not be $r0 or $r1
   38 |                 "csrxchg %[val], %[mask], %[reg]\n\t"
      |                 ^
<inline asm>:1:16: note: instantiated into assembly here
    1 |         csrxchg $a1, $ra, 0
      |                       ^


To prevent the compiler from allocating $r0 or $r1 for the "mask" of the
csrxchg instruction, the 'q' constraint must be used but Clang < 22 does
not support it. So force to use $t0 in the inline asm, in order to avoid
using $r0/$r1 while keeping the backward compatibility.

Cc: stable@vger.kernel.org
Link: https://github.com/llvm/llvm-project/pull/141037
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Suggested-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
V2: Update commit messages.

 arch/loongarch/include/asm/irqflags.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/include/asm/irqflags.h b/arch/loongarch/include/asm/irqflags.h
index 319a8c616f1f..003172b8406b 100644
--- a/arch/loongarch/include/asm/irqflags.h
+++ b/arch/loongarch/include/asm/irqflags.h
@@ -14,40 +14,48 @@
 static inline void arch_local_irq_enable(void)
 {
 	u32 flags = CSR_CRMD_IE;
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 }
 
 static inline void arch_local_irq_disable(void)
 {
 	u32 flags = 0;
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 }
 
 static inline unsigned long arch_local_irq_save(void)
 {
 	u32 flags = 0;
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 	return flags;
 }
 
 static inline void arch_local_irq_restore(unsigned long flags)
 {
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 }
 
-- 
2.47.1
Re: [PATCH V2] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by WANG Rui 6 months, 4 weeks ago 
On Sat, May 24, 2025 at 10:24 PM Huacai Chen <chenhuacai@loongson.cn> wrote:
>
> When building kernel with LLVM there are occasionally such errors:
>
> In file included from ./include/linux/spinlock.h:59:
> In file included from ./include/linux/irqflags.h:17:
> arch/loongarch/include/asm/irqflags.h:38:3: error: must not be $r0 or $r1
>    38 |                 "csrxchg %[val], %[mask], %[reg]\n\t"
>       |                 ^
> <inline asm>:1:16: note: instantiated into assembly here
>     1 |         csrxchg $a1, $ra, 0
>       |                       ^
>
>
> To prevent the compiler from allocating $r0 or $r1 for the "mask" of the
> csrxchg instruction, the 'q' constraint must be used but Clang < 22 does
> not support it. So force to use $t0 in the inline asm, in order to avoid
> using $r0/$r1 while keeping the backward compatibility.

Clang < 21

>
> Cc: stable@vger.kernel.org
> Link: https://github.com/llvm/llvm-project/pull/141037
> Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
> Suggested-by: WANG Rui <wangrui@loongson.cn>
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
> V2: Update commit messages.
>
>  arch/loongarch/include/asm/irqflags.h | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/irqflags.h b/arch/loongarch/include/asm/irqflags.h
> index 319a8c616f1f..003172b8406b 100644
> --- a/arch/loongarch/include/asm/irqflags.h
> +++ b/arch/loongarch/include/asm/irqflags.h
> @@ -14,40 +14,48 @@
>  static inline void arch_local_irq_enable(void)
>  {
>         u32 flags = CSR_CRMD_IE;
> +       register u32 mask asm("t0") = CSR_CRMD_IE;
> +
>         __asm__ __volatile__(
>                 "csrxchg %[val], %[mask], %[reg]\n\t"
>                 : [val] "+r" (flags)
> -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
>                 : "memory");
>  }
>
>  static inline void arch_local_irq_disable(void)
>  {
>         u32 flags = 0;
> +       register u32 mask asm("t0") = CSR_CRMD_IE;
> +
>         __asm__ __volatile__(
>                 "csrxchg %[val], %[mask], %[reg]\n\t"
>                 : [val] "+r" (flags)
> -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
>                 : "memory");
>  }
>
>  static inline unsigned long arch_local_irq_save(void)
>  {
>         u32 flags = 0;
> +       register u32 mask asm("t0") = CSR_CRMD_IE;
> +
>         __asm__ __volatile__(
>                 "csrxchg %[val], %[mask], %[reg]\n\t"
>                 : [val] "+r" (flags)
> -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
>                 : "memory");
>         return flags;
>  }
>
>  static inline void arch_local_irq_restore(unsigned long flags)
>  {
> +       register u32 mask asm("t0") = CSR_CRMD_IE;
> +
>         __asm__ __volatile__(
>                 "csrxchg %[val], %[mask], %[reg]\n\t"
>                 : [val] "+r" (flags)
> -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
>                 : "memory");
>  }
>
> --
> 2.47.1
>
>
Re: [PATCH V2] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by Huacai Chen 6 months, 4 weeks ago 
On Sun, May 25, 2025 at 10:01 AM WANG Rui <wangrui@loongson.cn> wrote:
>
> On Sat, May 24, 2025 at 10:24 PM Huacai Chen <chenhuacai@loongson.cn> wrote:
> >
> > When building kernel with LLVM there are occasionally such errors:
> >
> > In file included from ./include/linux/spinlock.h:59:
> > In file included from ./include/linux/irqflags.h:17:
> > arch/loongarch/include/asm/irqflags.h:38:3: error: must not be $r0 or $r1
> >    38 |                 "csrxchg %[val], %[mask], %[reg]\n\t"
> >       |                 ^
> > <inline asm>:1:16: note: instantiated into assembly here
> >     1 |         csrxchg $a1, $ra, 0
> >       |                       ^
> >
> >
> > To prevent the compiler from allocating $r0 or $r1 for the "mask" of the
> > csrxchg instruction, the 'q' constraint must be used but Clang < 22 does
> > not support it. So force to use $t0 in the inline asm, in order to avoid
> > using $r0/$r1 while keeping the backward compatibility.
>
> Clang < 21
OK, V3 sent.

Huacai
>
> >
> > Cc: stable@vger.kernel.org
> > Link: https://github.com/llvm/llvm-project/pull/141037
> > Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
> > Suggested-by: WANG Rui <wangrui@loongson.cn>
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> > V2: Update commit messages.
> >
> >  arch/loongarch/include/asm/irqflags.h | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/irqflags.h b/arch/loongarch/include/asm/irqflags.h
> > index 319a8c616f1f..003172b8406b 100644
> > --- a/arch/loongarch/include/asm/irqflags.h
> > +++ b/arch/loongarch/include/asm/irqflags.h
> > @@ -14,40 +14,48 @@
> >  static inline void arch_local_irq_enable(void)
> >  {
> >         u32 flags = CSR_CRMD_IE;
> > +       register u32 mask asm("t0") = CSR_CRMD_IE;
> > +
> >         __asm__ __volatile__(
> >                 "csrxchg %[val], %[mask], %[reg]\n\t"
> >                 : [val] "+r" (flags)
> > -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> > +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
> >                 : "memory");
> >  }
> >
> >  static inline void arch_local_irq_disable(void)
> >  {
> >         u32 flags = 0;
> > +       register u32 mask asm("t0") = CSR_CRMD_IE;
> > +
> >         __asm__ __volatile__(
> >                 "csrxchg %[val], %[mask], %[reg]\n\t"
> >                 : [val] "+r" (flags)
> > -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> > +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
> >                 : "memory");
> >  }
> >
> >  static inline unsigned long arch_local_irq_save(void)
> >  {
> >         u32 flags = 0;
> > +       register u32 mask asm("t0") = CSR_CRMD_IE;
> > +
> >         __asm__ __volatile__(
> >                 "csrxchg %[val], %[mask], %[reg]\n\t"
> >                 : [val] "+r" (flags)
> > -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> > +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
> >                 : "memory");
> >         return flags;
> >  }
> >
> >  static inline void arch_local_irq_restore(unsigned long flags)
> >  {
> > +       register u32 mask asm("t0") = CSR_CRMD_IE;
> > +
> >         __asm__ __volatile__(
> >                 "csrxchg %[val], %[mask], %[reg]\n\t"
> >                 : [val] "+r" (flags)
> > -               : [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
> > +               : [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
> >                 : "memory");
> >  }
> >
> > --
> > 2.47.1
> >
> >
>

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