Re: [PATCH] x86/mm: Remove in_nmi() warning from 64bit implementation of vmalloc_fault()

[Peter Zijlstra]

On Wed, Apr 24, 2019 at 09:04:57AM +0200, Jiri Kosina wrote:
> From: Jiri Kosina <jkosina@xxxxxxx>
> 
> In-NMI warnings have been added to vmalloc_fault() via ebc8827f75 ("x86: 
> Barf when vmalloc and kmemcheck faults happen in NMI") back in the time 
> when our NMI entry code could not cope with nested NMIs.
> 
> These days, it's perfectly fine to take a fault in NMI context and we 
> don't have to care about the fact that IRET from the fault handler might 
> cause NMI nesting.
> 
> This warning has already been removed from 32bit implementation of 
> vmalloc_fault() in 6863ea0cda8 ("x86/mm: Remove in_nmi() warning from 
> vmalloc_fault()"), but 64bit version was omitted.
> 
> Remove the bogus warning also from 64bit implementation of vmalloc_fault().

Cute; did you actually trigger this?

> Fixes: 6863ea0cda8 ("x86/mm: Remove in_nmi() warning from vmalloc_fault()")
> Reported-by: Nicolai Stange <nstange@xxxxxxx>
> Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

> ---
>  arch/x86/mm/fault.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 667f1da36208..5eaf67e8314f 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -359,8 +359,6 @@ static noinline int vmalloc_fault(unsigned long address)
>  	if (!(address >= VMALLOC_START && address < VMALLOC_END))
>  		return -1;
>  
> -	WARN_ON_ONCE(in_nmi());
> -
>  	/*
>  	 * Copy kernel mappings over when needed. This can also
>  	 * happen within a race in page table update. In the later
> 
> -- 
> Jiri Kosina
> SUSE Labs
>