[PATCH v4 07/28] vfio: powerpc/spapr: Moving pinning/unpinning to helpers

[Alexey Kardashevskiy]

This is a pretty mechanical patch to make next patches simpler.

New tce_iommu_unuse_page() helper does put_page() now but it might skip
that after the memory registering patch applied.

As we are here, this removes unnecessary checks for a value returned
by pfn_to_page() as it cannot possibly return NULL.

Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
---
 drivers/vfio/vfio_iommu_spapr_tce.c | 59 +++++++++++++++++++++++++++----------
 1 file changed, 44 insertions(+), 15 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 67ea392..7fd60f9 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -217,25 +217,34 @@ static void tce_iommu_release(void *iommu_data)
 	kfree(container);
 }
 
+static void tce_iommu_unuse_page(struct tce_container *container,
+		unsigned long oldtce)
+{
+	struct page *page;
+
+	if (!(oldtce & (TCE_PCI_READ | TCE_PCI_WRITE)))
+		return;
+
+	page = pfn_to_page(__pa(oldtce) >> PAGE_SHIFT);
+
+	if (oldtce & TCE_PCI_WRITE)
+		SetPageDirty(page);
+
+	put_page(page);
+}
+
 static int tce_iommu_clear(struct tce_container *container,
 		struct iommu_table *tbl,
 		unsigned long entry, unsigned long pages)
 {
 	unsigned long oldtce;
-	struct page *page;
 
 	for ( ; pages; --pages, ++entry) {
 		oldtce = iommu_clear_tce(tbl, entry);
 		if (!oldtce)
 			continue;
 
-		page = pfn_to_page(oldtce >> PAGE_SHIFT);
-		WARN_ON(!page);
-		if (page) {
-			if (oldtce & TCE_PCI_WRITE)
-				SetPageDirty(page);
-			put_page(page);
-		}
+		tce_iommu_unuse_page(container, (unsigned long) __va(oldtce));
 	}
 
 	return 0;
@@ -253,34 +262,54 @@ static enum dma_data_direction tce_iommu_direction(unsigned long tce)
 		return DMA_NONE;
 }
 
+static unsigned long tce_get_hva(struct tce_container *container,
+		unsigned page_shift, unsigned long tce)
+{
+	long ret;
+	struct page *page = NULL;
+	unsigned long hva;
+	enum dma_data_direction direction = tce_iommu_direction(tce);
+
+	ret = get_user_pages_fast(tce & PAGE_MASK, 1,
+			direction != DMA_TO_DEVICE, &page);
+	if (unlikely(ret != 1))
+		return -1;
+
+	hva = (unsigned long) page_address(page);
+
+	return hva;
+}
+
 static long tce_iommu_build(struct tce_container *container,
 		struct iommu_table *tbl,
 		unsigned long entry, unsigned long tce, unsigned long pages)
 {
 	long i, ret = 0;
-	struct page *page = NULL;
+	struct page *page;
 	unsigned long hva;
 	enum dma_data_direction direction = tce_iommu_direction(tce);
 
 	for (i = 0; i < pages; ++i) {
-		ret = get_user_pages_fast(tce & PAGE_MASK, 1,
-				direction != DMA_TO_DEVICE, &page);
-		if (unlikely(ret != 1)) {
+		hva = tce_get_hva(container, tbl->it_page_shift, tce);
+		if (hva == -1) {
 			ret = -EFAULT;
 			break;
 		}
 
+		page = pfn_to_page(__pa(hva) >> PAGE_SHIFT);
 		if (!tce_page_is_contained(page, tbl->it_page_shift)) {
 			ret = -EPERM;
 			break;
 		}
 
-		hva = (unsigned long) page_address(page) +
-			(tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK);
+		/* Preserve offset within IOMMU page */
+		hva |= tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK;
+		/* Preserve permission bits */
+		hva |= tce & (TCE_PCI_READ | TCE_PCI_WRITE);
 
 		ret = iommu_tce_build(tbl, entry + i, hva, direction);
 		if (ret) {
-			put_page(page);
+			tce_iommu_unuse_page(container, hva);
 			pr_err("iommu_tce: %s failed ioba=%lx, tce=%lx, ret=%ld\n",
 					__func__, entry << tbl->it_page_shift,
 					tce, ret);
-- 
2.0.0

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