Re: [PATCH v1 03/10] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc

Alexey Kardashevskiy
2020-08-22T10:10:06Z

On 18/08/2020 09:40, Leonardo Bras wrote:
> As of today, doing iommu_range_alloc() only for !largealloc (npages <= 15)
> will only be able to use 3/4 of the available pages, given pages on
> largepool not being available for !largealloc.
>
> This could mean some drivers not being able to fully use all the available
> pages for the DMA window.
>
> Add pages on largepool as a last resort for !largealloc, making all pages
> of the DMA window available.
>
> Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
> ---
> arch/powerpc/kernel/iommu.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index d7086087830f..7f603d4e62d4 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -261,6 +261,15 @@ static unsigned long iommu_range_alloc(struct device *dev,
> pass++;
> goto again;
>
> + } else if (pass == tbl->nr_pools + 1) {
> + /* Last resort: try largepool */
> + spin_unlock(&pool->lock);
> + pool = &tbl->large_pool;
> + spin_lock(&pool->lock);
> + pool->hint = pool->start;
> + pass++;
> + goto again;
> +

A nit: unnecessary new line.

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

> } else {
> /* Give up */
> spin_unlock_irqrestore(&(pool->lock), flags);
>

--
Alexey