Re: [PATCH 1/4] mm: Correct ordering of *_clear_flush_young_notify

[Paolo Bonzini <pbonzini@redhat.com>]

Andrea, Rik, please review this patch.

Thanks in advance,

Paolo

On 08/01/2015 12:59, Marc Zyngier wrote:
> From: Steve Capper <steve.capper@linaro.org>
> 
> ptep_clear_flush_young_notify and pmdp_clear_flush_young_notify both
> call the notifiers *after* the pte/pmd has been made young.
> 
> This can cause problems with KVM that relies on being able to block
> MMU notifiers when carrying out maintenance of second stage
> descriptors.
> 
> This patch ensures that the MMU notifiers are called before ptes and
> pmds are made old.
> 
> Signed-off-by: Steve Capper <steve.capper@linaro.org>
> ---
>  include/linux/mmu_notifier.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> index 95243d2..c454c76 100644
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -290,11 +290,11 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
>  	int __young;							\
>  	struct vm_area_struct *___vma = __vma;				\
>  	unsigned long ___address = __address;				\
> -	__young = ptep_clear_flush_young(___vma, ___address, __ptep);	\
> -	__young |= mmu_notifier_clear_flush_young(___vma->vm_mm,	\
> +	__young = mmu_notifier_clear_flush_young(___vma->vm_mm,		\
>  						  ___address,		\
>  						  ___address +		\
>  							PAGE_SIZE);	\
> +	__young |= ptep_clear_flush_young(___vma, ___address, __ptep);	\
>  	__young;							\
>  })
>  
> @@ -303,11 +303,11 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
>  	int __young;							\
>  	struct vm_area_struct *___vma = __vma;				\
>  	unsigned long ___address = __address;				\
> -	__young = pmdp_clear_flush_young(___vma, ___address, __pmdp);	\
> -	__young |= mmu_notifier_clear_flush_young(___vma->vm_mm,	\
> +	__young = mmu_notifier_clear_flush_young(___vma->vm_mm,		\
>  						  ___address,		\
>  						  ___address +		\
>  							PMD_SIZE);	\
> +	__young |= pmdp_clear_flush_young(___vma, ___address, __pmdp);	\
>  	__young;							\
>  })
>  
>