2021-03-18 17:47:28

by Leonardo Brás

Subject: [PATCH 1/1] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc

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 <[email protected]>
Reviewed-by: Alexey Kardashevskiy <[email protected]>
---
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 3329ef045805..ae6ad8dca605 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -255,6 +255,15 @@ 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;
+
} else {
/* Give up */
spin_unlock_irqrestore(&(pool->lock), flags);
--
2.29.2

2021-04-22 06:52:55

by Leonardo Brás

Subject: Re: [PATCH 1/1] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc

Hello,

FYI: This patch was reviewed when it was part of another patchset:
http://patchwork.ozlabs.org/project/linuxppc-dev/patch/[email protected]/


On Thu, 2021-03-18 at 14:44 -0300, 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 <[email protected]>
> Reviewed-by: Alexey Kardashevskiy <[email protected]>
> ---
>  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 3329ef045805..ae6ad8dca605 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -255,6 +255,15 @@ 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;
> +
>   } else {
>   /* Give up */
>   spin_unlock_irqrestore(&(pool->lock), flags);

2021-04-29 14:04:43

by Michael Ellerman

Subject: Re: [PATCH 1/1] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc

On Thu, 18 Mar 2021 14:44:17 -0300, 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.
>
> [...]

Applied to powerpc/next.

[1/1] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc
https://git.kernel.org/powerpc/c/fc5590fd56c9608f317729b59a56dad2a75d633f

cheers