Re: [Xen-devel] Is: x86: mm: Fix vmalloc_fault oops during lazy MMU updates Was: Re: [PATCH] mm/x86: Flush lazy MMU when DEBUG_PAGEALLOC is set

[Borislav Petkov <bp@xxxxxxxxx>]

On Thu, Feb 28, 2013 at 09:29:10AM -0500, Konrad Rzeszutek Wilk wrote:
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index fb674fd..4f7d793 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -378,10 +378,12 @@ static noinline __kprobes int vmalloc_fault(unsigned 
> long address)
>       if (pgd_none(*pgd_ref))
>               return -1;
>  
> -     if (pgd_none(*pgd))
> +     if (pgd_none(*pgd)) {
>               set_pgd(pgd, *pgd_ref);
> -     else
> +             arch_flush_lazy_mmu_mode();

Do I understand it correctly that this would cost us a
"preempt_disable(); preempt_enable()" needlessly on baremetal when
running with CONFIG_PARAVIRT enabled?

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--

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