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

Huacai Chen posted 1 patch 6 months, 3 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There is a newer version of this series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] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by Huacai Chen 6 months, 3 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
      |                       ^

The "mask" of the csrxchg instruction should not be $r0 or $r1, but the
compiler cannot avoid generating such code currently. So force to use t0
in the inline asm, in order to avoid using $r0/$r1.

Cc: stable@vger.kernel.org
Suggested-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 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] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by Yanteng Si 6 months, 3 weeks ago 
在 5/22/25 8:50 PM, Huacai Chen 写道:
> 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
>        |                       ^
> 
> The "mask" of the csrxchg instruction should not be $r0 or $r1, but the
> compiler cannot avoid generating such code currently. So force to use t0
> in the inline asm, in order to avoid using $r0/$r1.
> 
> Cc: stable@vger.kernel.org
> Suggested-by: WANG Rui <wangrui@loongson.cn>
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>

Thanks,
Yanteng
> ---
>   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");
>   }
>
Re: [PATCH] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by Xi Ruoyao 6 months, 3 weeks ago 
On Thu, 2025-05-22 at 20:50 +0800, Huacai Chen 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
>       |                       ^
> 
> The "mask" of the csrxchg instruction should not be $r0 or $r1, but the
> compiler cannot avoid generating such code currently.

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

And Link: https://github.com/llvm/llvm-project/pull/141037

> So force to use t0
> in the inline asm, in order to avoid using $r0/$r1.
> 
> Cc: stable@vger.kernel.org
> Suggested-by: WANG Rui <wangrui@loongson.cn>
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
>  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");
>  }
>  

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
Re: [PATCH] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
Posted by Huacai Chen 6 months, 3 weeks ago 
On Fri, May 23, 2025 at 12:38 PM Xi Ruoyao <xry111@xry111.site> wrote:
>
> On Thu, 2025-05-22 at 20:50 +0800, Huacai Chen 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
> >       |                       ^
> >
> > The "mask" of the csrxchg instruction should not be $r0 or $r1, but the
> > compiler cannot avoid generating such code currently.
>
> Maybe "to prevent the compiler from allocating $r0 or $r1, the 'q'
> constraint must be used but Clang < 22 does not support it.  So force to
> use t0 in order to avoid using $r0/$r1 while keeping the backward
> compatibility."
>
> And Link: https://github.com/llvm/llvm-project/pull/141037
OK, that's better.

Huacai

>
> > So force to use t0
> > in the inline asm, in order to avoid using $r0/$r1.
> >
> > Cc: stable@vger.kernel.org
> > Suggested-by: WANG Rui <wangrui@loongson.cn>
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >  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");
> >  }
> >
>
> --
> Xi Ruoyao <xry111@xry111.site>
> School of Aerospace Science and Technology, Xidian University

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