[PATCH] Revert "powerpc/kernel/iommu: Align size for IOMMU_PAGE_SIZE() to save TCEs"

[Alexey Kardashevskiy]

On 27/05/2021 00:45, Frederic Barrat wrote:
> This reverts commit 3c0468d4451eb6b4f6604370639f163f9637a479.
> 
> That commit was breaking alignment guarantees for the DMA address when
> allocating coherent mappings, as described in
> Documentation/core-api/dma-api-howto.rst
> 
> It was also noticed by Mellanox' driver:
> [ 1515.763621] mlx5_core c002:01:00.0: mlx5_frag_buf_alloc_node:146:(pid 13402): unexpected map alignment: 0x0800000000c61000, page_shift=16
> [ 1515.763635] mlx5_core c002:01:00.0: mlx5_cqwq_create:181:(pid
> 13402): mlx5_frag_buf_alloc_node() failed, -12
> 
> Signed-off-by: Frederic Barrat <fbarrat at linux.ibm.com>

Should it be

Fixes: 3c0468d4451e ("powerpc/kernel/iommu: Align size for 
IOMMU_PAGE_SIZE() to save TCEs")

?

Anyway,

Reviewed-by: Alexey Kardashevskiy <aik at ozlabs.ru>

I should have known better in the first place, sorry :-/ Thanks,


> ---
>   arch/powerpc/kernel/iommu.c | 11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 57d6b85e9b96..2af89a5e379f 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -898,7 +898,6 @@ void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
>   	unsigned int order;
>   	unsigned int nio_pages, io_order;
>   	struct page *page;
> -	size_t size_io = size;
>   
>   	size = PAGE_ALIGN(size);
>   	order = get_order(size);
> @@ -925,9 +924,8 @@ void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
>   	memset(ret, 0, size);
>   
>   	/* Set up tces to cover the allocated range */
> -	size_io = IOMMU_PAGE_ALIGN(size_io, tbl);
> -	nio_pages = size_io >> tbl->it_page_shift;
> -	io_order = get_iommu_order(size_io, tbl);
> +	nio_pages = size >> tbl->it_page_shift;
> +	io_order = get_iommu_order(size, tbl);
>   	mapping = iommu_alloc(dev, tbl, ret, nio_pages, DMA_BIDIRECTIONAL,
>   			      mask >> tbl->it_page_shift, io_order, 0);
>   	if (mapping == DMA_MAPPING_ERROR) {
> @@ -942,9 +940,10 @@ void iommu_free_coherent(struct iommu_table *tbl, size_t size,
>   			 void *vaddr, dma_addr_t dma_handle)
>   {
>   	if (tbl) {
> -		size_t size_io = IOMMU_PAGE_ALIGN(size, tbl);
> -		unsigned int nio_pages = size_io >> tbl->it_page_shift;
> +		unsigned int nio_pages;
>   
> +		size = PAGE_ALIGN(size);
> +		nio_pages = size >> tbl->it_page_shift;
>   		iommu_free(tbl, dma_handle, nio_pages);
>   		size = PAGE_ALIGN(size);
>   		free_pages((unsigned long)vaddr, get_order(size));
> 

-- 
Alexey