[v1,09/14] vfio/type1: Refactor pfn_list clearing

Commit Message

Alex Williamson March 8, 2021, 9:48 p.m. UTC

Pull code out to a function for re-use.

Signed-off-by: Alex Williamson <[e-mail]>
---
 drivers/vfio/vfio_iommu_type1.c |   57 +++++++++++++++++++++++----------------
 1 file changed, 34 insertions(+), 23 deletions(-)

Comments

Christoph Hellwig March 10, 2021, 8:01 a.m. UTC | #1

> +/* Return 1 if iommu->lock dropped and notified, 0 if done */

A bool would be more useful for that pattern.

> +static int unmap_dma_pfn_list(struct vfio_iommu *iommu, struct vfio_dma *dma,
> +			      struct vfio_dma **dma_last, int *retries)
> +{
> +	if (!RB_EMPTY_ROOT(&dma->pfn_list)) {

Just return early when it is empty to remove a level of indentation for
the whole function?

> +		struct vfio_iommu_type1_dma_unmap nb_unmap;
> +
> +		if (*dma_last == dma) {
> +			BUG_ON(++(*retries) > 10);
> +		} else {
> +			*dma_last = dma;
> +			*retries = 0;
> +		}
> +
> +		nb_unmap.iova = dma->iova;
> +		nb_unmap.size = dma->size;
> +
> +		/*
> +		 * Notify anyone (mdev vendor drivers) to invalidate and
> +		 * unmap iovas within the range we're about to unmap.
> +		 * Vendor drivers MUST unpin pages in response to an
> +		 * invalidation.
> +		 */
> +		mutex_unlock(&iommu->lock);
> +		blocking_notifier_call_chain(&iommu->notifier,
> +					     VFIO_IOMMU_NOTIFY_DMA_UNMAP,
> +					     &nb_unmap);
> +		return 1;

Conditional locking is a horrible pattern.  I'd rather only factor the
code until before the unlock into the helper, and then leave the
unlock and notify to the caller to avoid that anti-pattern.

Also vendor driver isn't really Linux terminology for a subdriver,
so I'd suggest to switch to something else while you're at it.

Patch

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 12d9905b429f..f7d35a114354 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -542,6 +542,39 @@  static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
 	return ret;
 }
 
+/* Return 1 if iommu->lock dropped and notified, 0 if done */
+static int unmap_dma_pfn_list(struct vfio_iommu *iommu, struct vfio_dma *dma,
+			      struct vfio_dma **dma_last, int *retries)
+{
+	if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
+		struct vfio_iommu_type1_dma_unmap nb_unmap;
+
+		if (*dma_last == dma) {
+			BUG_ON(++(*retries) > 10);
+		} else {
+			*dma_last = dma;
+			*retries = 0;
+		}
+
+		nb_unmap.iova = dma->iova;
+		nb_unmap.size = dma->size;
+
+		/*
+		 * Notify anyone (mdev vendor drivers) to invalidate and
+		 * unmap iovas within the range we're about to unmap.
+		 * Vendor drivers MUST unpin pages in response to an
+		 * invalidation.
+		 */
+		mutex_unlock(&iommu->lock);
+		blocking_notifier_call_chain(&iommu->notifier,
+					     VFIO_IOMMU_NOTIFY_DMA_UNMAP,
+					     &nb_unmap);
+		return 1;
+	}
+
+	return 0;
+}
+
 /*
  * Returns the positive number of pfns successfully obtained or a negative
  * error code.
@@ -1397,29 +1430,7 @@  static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 			continue;
 		}
 
-		if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
-			struct vfio_iommu_type1_dma_unmap nb_unmap;
-
-			if (dma_last == dma) {
-				BUG_ON(++retries > 10);
-			} else {
-				dma_last = dma;
-				retries = 0;
-			}
-
-			nb_unmap.iova = dma->iova;
-			nb_unmap.size = dma->size;
-
-			/*
-			 * Notify anyone (mdev vendor drivers) to invalidate and
-			 * unmap iovas within the range we're about to unmap.
-			 * Vendor drivers MUST unpin pages in response to an
-			 * invalidation.
-			 */
-			mutex_unlock(&iommu->lock);
-			blocking_notifier_call_chain(&iommu->notifier,
-						    VFIO_IOMMU_NOTIFY_DMA_UNMAP,
-						    &nb_unmap);
+		if (unmap_dma_pfn_list(iommu, dma, &dma_last, &retries)) {
 			mutex_lock(&iommu->lock);
 			goto again;
 		}