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[v2,4/6] iommu: Add granule_ignore when tlb gather

Message ID 20201119061836.15238-5-yong.wu@mediatek.com (mailing list archive)
State New
Headers show
Series MediaTek IOMMU improve tlb flush performance in map/unmap | expand

Commit Message

Yong Wu Nov. 19, 2020, 6:18 a.m. UTC
Add a granule_ignore option when tlb gather for some HW which don't care
about granule when it flush tlb.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
---
 include/linux/iommu.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Robin Murphy Nov. 25, 2020, 4:38 p.m. UTC | #1
On 2020-11-19 06:18, Yong Wu wrote:
> Add a granule_ignore option when tlb gather for some HW which don't care
> about granule when it flush tlb.
> 
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
>   include/linux/iommu.h | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 794d4085edd3..1aad32238510 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -171,6 +171,7 @@ enum iommu_dev_features {
>    * @start: IOVA representing the start of the range to be flushed
>    * @end: IOVA representing the end of the range to be flushed (exclusive)
>    * @pgsize: The interval at which to perform the flush
> + * @granule_ignore: For tlb flushing that could be regardless of granule.
>    *
>    * This structure is intended to be updated by multiple calls to the
>    * ->unmap() function in struct iommu_ops before eventually being passed
> @@ -180,6 +181,7 @@ struct iommu_iotlb_gather {
>   	unsigned long		start;
>   	unsigned long		end;
>   	size_t			pgsize;
> +	bool			granule_ignore;

I can't see that this would ever need to vary on a per-unmap-operation 
basis, so this doesn't seem like the right level of abstraction. AFAICS 
it should simply be hard-coded in the driver logic.

>   };
>   
>   /**
> @@ -544,7 +546,7 @@ static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
>   	 * a different granularity, then sync the TLB so that the gather
>   	 * structure can be rewritten.
>   	 */
> -	if (gather->pgsize != size ||
> +	if ((!gather->granule_ignore && gather->pgsize != size) ||

I also think this is a slippery slope in the wrong direction anyway - 
there is likely to be a fair bit of hardware-dependent variation around 
how low-level TLB maintenance works (also consider drivers that may want 
to convert a sufficiently large range to an "invalidate all" operation), 
so if a generic helper function doesn't do the right thing for a given 
driver, that driver should simply not use the helper, and directly 
implement the logic it does need.

Robin.

>   	    end < gather->start || start > gather->end) {
>   		if (gather->pgsize)
>   			iommu_iotlb_sync(domain, gather);
>
diff mbox series

Patch

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 794d4085edd3..1aad32238510 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -171,6 +171,7 @@  enum iommu_dev_features {
  * @start: IOVA representing the start of the range to be flushed
  * @end: IOVA representing the end of the range to be flushed (exclusive)
  * @pgsize: The interval at which to perform the flush
+ * @granule_ignore: For tlb flushing that could be regardless of granule.
  *
  * This structure is intended to be updated by multiple calls to the
  * ->unmap() function in struct iommu_ops before eventually being passed
@@ -180,6 +181,7 @@  struct iommu_iotlb_gather {
 	unsigned long		start;
 	unsigned long		end;
 	size_t			pgsize;
+	bool			granule_ignore;
 };
 
 /**
@@ -544,7 +546,7 @@  static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 	 * a different granularity, then sync the TLB so that the gather
 	 * structure can be rewritten.
 	 */
-	if (gather->pgsize != size ||
+	if ((!gather->granule_ignore && gather->pgsize != size) ||
 	    end < gather->start || start > gather->end) {
 		if (gather->pgsize)
 			iommu_iotlb_sync(domain, gather);