[PATCH kernel v12 11/34] vfio: powerpc/spapr: Moving pinning/unpinning to helpers

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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.

This moves tce_iommu_disable() later to let tce_iommu_clear() know if
the container has been enabled because if it has not been, then
put_page() must not be called on TCEs from the TCE table. This situation
is not yet possible but it will after KVM acceleration patchset is
applied.

This changes code to work with physical addresses rather than linear
mapping addresses for better code readability. Following patches will
add an xchg() callback for an IOMMU table which will accept/return
physical addresses (unlike current tce_build()) which will eliminate
redundant conversions.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[aw: for the vfio related changes]
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
---
Changes:
v9:
* changed helpers to work with physical addresses rather than linear
(for simplicity - later ::xchg() will receive physical and avoid
additional convertions)

v6:
* tce_get_hva() returns hva via a pointer
---
 drivers/vfio/vfio_iommu_spapr_tce.c | 61 +++++++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 20 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 5bbdf37..cf5d4a1 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -191,69 +191,90 @@ static void tce_iommu_release(void *iommu_data)
 	struct tce_container *container = iommu_data;
 
 	WARN_ON(container->tbl && !container->tbl->it_group);
-	tce_iommu_disable(container);
 
 	if (container->tbl && container->tbl->it_group)
 		tce_iommu_detach_group(iommu_data, container->tbl->it_group);
 
+	tce_iommu_disable(container);
 	mutex_destroy(&container->lock);
 
 	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(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, oldtce);
 	}
 
 	return 0;
 }
 
+static int tce_iommu_use_page(unsigned long tce, unsigned long *hpa)
+{
+	struct page *page = NULL;
+	enum dma_data_direction direction = iommu_tce_direction(tce);
+
+	if (get_user_pages_fast(tce & PAGE_MASK, 1,
+			direction != DMA_TO_DEVICE, &page) != 1)
+		return -EFAULT;
+
+	*hpa = __pa((unsigned long) page_address(page));
+
+	return 0;
+}
+
 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;
-	unsigned long hva;
+	struct page *page;
+	unsigned long hpa;
 	enum dma_data_direction direction = iommu_tce_direction(tce);
 
 	for (i = 0; i < pages; ++i) {
 		unsigned long offset = tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK;
 
-		ret = get_user_pages_fast(tce & PAGE_MASK, 1,
-				direction != DMA_TO_DEVICE, &page);
-		if (unlikely(ret != 1)) {
-			ret = -EFAULT;
+		ret = tce_iommu_use_page(tce, &hpa);
+		if (ret)
 			break;
-		}
 
+		page = pfn_to_page(hpa >> PAGE_SHIFT);
 		if (!tce_page_is_contained(page, tbl->it_page_shift)) {
 			ret = -EPERM;
 			break;
 		}
 
-		hva = (unsigned long) page_address(page) + offset;
-
-		ret = iommu_tce_build(tbl, entry + i, hva, direction);
+		hpa |= offset;
+		ret = iommu_tce_build(tbl, entry + i, (unsigned long) __va(hpa),
+				direction);
 		if (ret) {
-			put_page(page);
+			tce_iommu_unuse_page(container, hpa);
 			pr_err("iommu_tce: %s failed ioba=%lx, tce=%lx, ret=%ld\n",
 					__func__, entry << tbl->it_page_shift,
 					tce, ret);
-- 
2.4.0.rc3.8.gfb3e7d5