Re: [PATCH kernel v5 3/6] vfio/spapr: Postpone allocation of userspace version of TCE table

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Nov 11, 2016 at 11:32:14PM +1100, Alexey Kardashevskiy wrote:
> The iommu_table struct manages a hardware TCE table and a vmalloc'd
> table with corresponding userspace addresses. Both are allocated when
> the default DMA window is created and this happens when the very first
> group is attached to a container.
> 
> As we are going to allow the userspace to configure container in one
> memory context and pas container fd to another, we have to postpones
> such allocations till a container fd is passed to the destination
> user process so we would account locked memory limit against the actual
> container user constrainsts.
> 
> This postpones the it_userspace array allocation till it is used first
> time for mapping. The unmapping patch already checks if the array is
> allocated.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  drivers/vfio/vfio_iommu_spapr_tce.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index d0c38b2..442baac 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -515,6 +515,12 @@ static long tce_iommu_build_v2(struct tce_container *container,
>  	unsigned long hpa;
>  	enum dma_data_direction dirtmp;
>  
> +	if (!tbl->it_userspace) {
> +		ret = tce_iommu_userspace_view_alloc(tbl);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	for (i = 0; i < pages; ++i) {
>  		struct mm_iommu_table_group_mem_t *mem = NULL;
>  		unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl,
> @@ -1068,10 +1074,7 @@ static int tce_iommu_take_ownership(struct tce_container *container,
>  		if (!tbl || !tbl->it_map)
>  			continue;
>  
> -		rc = tce_iommu_userspace_view_alloc(tbl);
> -		if (!rc)
> -			rc = iommu_take_ownership(tbl);
> -
> +		rc = iommu_take_ownership(tbl);
>  		if (rc) {
>  			for (j = 0; j < i; ++j)
>  				iommu_release_ownership(

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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