Re: [PATCH] powerpc: Correct VIO bus accounting problem in CMO env.

[Brian King <brking@linux.vnet.ibm.com>]

Acked by: Brian King <brking@linux.vnet.ibm.com>

Robert Jennings wrote:
> In the VIO bus code the wrappers for dma alloc_coherent and free_coherent
> calls are rounding to IOMMU_PAGE_SIZE.  Taking a look at the underlying
> calls, the actual mapping is promoted to PAGE_SIZE.  Changing the
> rounding in these two functions fixes under-reporting the entitlement
> used by the system.  Without this change, the system could run out of
> entitlement before it believes it has and incur mapping failures at the
> firmware level.
> 
> Also in the VIO bus code, the wrapper for dma map_sg is not exiting in
> an error path where it should.  Rather than fall through to code for the
> success case, this patch adds the return that is needed in the error path.
> 
> Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
> 
> ---
>  arch/powerpc/kernel/vio.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> Index: b/arch/powerpc/kernel/vio.c
> ===================================================================
> --- a/arch/powerpc/kernel/vio.c
> +++ b/arch/powerpc/kernel/vio.c
> @@ -492,14 +492,14 @@ static void *vio_dma_iommu_alloc_coheren
>  	struct vio_dev *viodev = to_vio_dev(dev);
>  	void *ret;
> 
> -	if (vio_cmo_alloc(viodev, roundup(size, IOMMU_PAGE_SIZE))) {
> +	if (vio_cmo_alloc(viodev, roundup(size, PAGE_SIZE))) {
>  		atomic_inc(&viodev->cmo.allocs_failed);
>  		return NULL;
>  	}
> 
>  	ret = dma_iommu_ops.alloc_coherent(dev, size, dma_handle, flag);
>  	if (unlikely(ret == NULL)) {
> -		vio_cmo_dealloc(viodev, roundup(size, IOMMU_PAGE_SIZE));
> +		vio_cmo_dealloc(viodev, roundup(size, PAGE_SIZE));
>  		atomic_inc(&viodev->cmo.allocs_failed);
>  	}
> 
> @@ -513,7 +513,7 @@ static void vio_dma_iommu_free_coherent(
> 
>  	dma_iommu_ops.free_coherent(dev, size, vaddr, dma_handle);
> 
> -	vio_cmo_dealloc(viodev, roundup(size, IOMMU_PAGE_SIZE));
> +	vio_cmo_dealloc(viodev, roundup(size, PAGE_SIZE));
>  }
> 
>  static dma_addr_t vio_dma_iommu_map_page(struct device *dev, struct page *page,
> @@ -572,6 +572,7 @@ static int vio_dma_iommu_map_sg(struct d
>  	if (unlikely(!ret)) {
>  		vio_cmo_dealloc(viodev, alloc_size);
>  		atomic_inc(&viodev->cmo.allocs_failed);
> +		return ret;
>  	}
> 
>  	for (sgl = sglist, count = 0; count < ret; count++, sgl++)
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-- 
Brian King
Linux on Power Virtualization
IBM Linux Technology Center