Linux Virtualization - Aug 2020 - [PATCH] x86/paravirt: Add missing noinstr to arch_local*() helpers

On Wed, Aug 05, 2020 at 03:26:29PM +0200, Marco Elver
wrote:
> Add missing noinstr to arch_local*() helpers, as they may be called from
> noinstr code.
> 
> On a KCSAN config with CONFIG_PARAVIRT=y, syzbot stumbled across corrupt
Cute, so I've been working on adding objtool support for this a little:

  https://lkml.kernel.org/r/20200803143231.GE2674 at
hirez.programming.kicks-ass.net
> diff --git a/arch/x86/include/asm/paravirt.h
b/arch/x86/include/asm/paravirt.h
> index 3d2afecde50c..a606f2ba2b5e 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -760,27 +760,27 @@ bool
__raw_callee_save___native_vcpu_is_preempted(long cpu);
>  	((struct paravirt_callee_save) { func })
>  
>  #ifdef CONFIG_PARAVIRT_XXL
> -static inline notrace unsigned long arch_local_save_flags(void)
> +static inline noinstr unsigned long arch_local_save_flags(void)
>  {
>  	return PVOP_CALLEE0(unsigned long, irq.save_fl);
>  }
>  
> -static inline notrace void arch_local_irq_restore(unsigned long f)
> +static inline noinstr void arch_local_irq_restore(unsigned long f)
>  {
>  	PVOP_VCALLEE1(irq.restore_fl, f);
>  }
>  
> -static inline notrace void arch_local_irq_disable(void)
> +static inline noinstr void arch_local_irq_disable(void)
>  {
>  	PVOP_VCALLEE0(irq.irq_disable);
>  }
>  
> -static inline notrace void arch_local_irq_enable(void)
> +static inline noinstr void arch_local_irq_enable(void)
>  {
>  	PVOP_VCALLEE0(irq.irq_enable);
>  }
>  
> -static inline notrace unsigned long arch_local_irq_save(void)
> +static inline noinstr unsigned long arch_local_irq_save(void)
>  {
>  	unsigned long f;
>  
Shouldn't we __always_inline those? They're going to be really small.