Subject: Re: [PATCH kernel v7 04/31] vfio: powerpc/spapr: Use it_page_size

From: Alex Williamson <[email-masked]>
Date: Wed, 01 Apr 2015 15:48:24 -0600

On Sat, 2015-03-28 at 01:54 +1100, Alexey Kardashevskiy wrote:
> This makes use of the it_page_size from the iommu_table struct
> as page size can differ.
> 
> This replaces missing IOMMU_PAGE_SHIFT macro in commented debug code
> as recently introduced IOMMU_PAGE_XXX macros do not include
> IOMMU_PAGE_SHIFT.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> Reviewed-by: David Gibson <[email-masked]>
> ---
>  drivers/vfio/vfio_iommu_spapr_tce.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index f835e63..8bbee22 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -91,7 +91,7 @@ static int tce_iommu_enable(struct tce_container *container)
>  	 * enforcing the limit based on the max that the guest can map.
>  	 */
>  	down_write(&current->mm->mmap_sem);
> -	npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
> +	npages = (tbl->it_size << tbl->it_page_shift) >> PAGE_SHIFT;
>  	locked = current->mm->locked_vm + npages;
>  	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>  	if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
> @@ -120,7 +120,7 @@ static void tce_iommu_disable(struct tce_container *container)
>  
>  	down_write(&current->mm->mmap_sem);
>  	current->mm->locked_vm -= (container->tbl->it_size <<
> -			IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
> +			container->tbl->it_page_shift) >> PAGE_SHIFT;
>  	up_write(&current->mm->mmap_sem);
>  }
>  
> @@ -222,7 +222,7 @@ static long tce_iommu_build(struct tce_container *container,
>  					tce, ret);
>  			break;
>  		}
> -		tce += IOMMU_PAGE_SIZE_4K;
> +		tce += IOMMU_PAGE_SIZE(tbl);

Is PAGE_SIZE ever smaller than IOMMU_PAGE_SIZE(tbl)?  IOW, can the page
we got from get_user_pages_fast() ever not completely fill the tce
entry?

(Have I asked this before?  Sorry if so)