[PATCH v11 Kernel 6/6] vfio: Selective dirty page tracking if IOMMU backed device pins pages

[Kirti Wankhede <kwankhede@nvidia.com>]

Track dirty pages reporting capability for each vfio_device by setting the
capability flag on calling vfio_pin_pages() for that device.

In vfio_iommu_type1 module, while creating dirty pages bitmap, check if
IOMMU backed device is present in the container. If IOMMU backed device is
present in container then check dirty pages reporting capability for each
vfio device in the container. If all vfio devices are capable of reporing
dirty pages tracking by pinning pages through external API, then report
create bitmap of pinned pages only. If IOMMU backed device is present in
the container and any one device is not able to report dirty pages, then
marked all pages as dirty.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio.c             | 33 +++++++++++++++++++++++++++++++
 drivers/vfio/vfio_iommu_type1.c | 44 +++++++++++++++++++++++++++++++++++++++--
 include/linux/vfio.h            |  3 ++-
 3 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c8482624ca34..9d2fbe09768a 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -96,6 +96,8 @@ struct vfio_device {
 	struct vfio_group		*group;
 	struct list_head		group_next;
 	void				*device_data;
+	/* dirty pages reporting capable */
+	bool				dirty_pages_cap;
 };
 
 #ifdef CONFIG_VFIO_NOIOMMU
@@ -1866,6 +1868,29 @@ int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, int num_irqs,
 }
 EXPORT_SYMBOL(vfio_set_irqs_validate_and_prepare);
 
+int vfio_device_is_dirty_reporting_capable(struct device *dev, bool *cap)
+{
+	struct vfio_device *device;
+	struct vfio_group *group;
+
+	if (!dev || !cap)
+		return -EINVAL;
+
+	group = vfio_group_get_from_dev(dev);
+	if (!group)
+		return -ENODEV;
+
+	device = vfio_group_get_device(group, dev);
+	if (!device)
+		return -ENODEV;
+
+	*cap = device->dirty_pages_cap;
+	vfio_device_put(device);
+	vfio_group_put(group);
+	return 0;
+}
+EXPORT_SYMBOL(vfio_device_is_dirty_reporting_capable);
+
 /*
  * Pin a set of guest PFNs and return their associated host PFNs for local
  * domain only.
@@ -1907,6 +1932,14 @@ int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage,
 	else
 		ret = -ENOTTY;
 
+	if (ret > 0) {
+		struct vfio_device *device = vfio_group_get_device(group, dev);
+
+		if (device) {
+			device->dirty_pages_cap = true;
+			vfio_device_put(device);
+		}
+	}
 	vfio_group_try_dissolve_container(group);
 
 err_pin_pages:
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 68d8ed3b2665..ef56f31f4e73 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -891,6 +891,39 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
 	return bitmap;
 }
 
+static int vfio_is_dirty_pages_reporting_capable(struct device *dev, void *data)
+{
+	bool new;
+	int ret;
+
+	ret = vfio_device_is_dirty_reporting_capable(dev, &new);
+	if (ret)
+		return ret;
+
+	*(bool *)data = *(bool *)data && new;
+
+	return 0;
+}
+
+static bool vfio_dirty_pages_reporting_capable(struct vfio_iommu *iommu)
+{
+	struct vfio_domain *d;
+	struct vfio_group *g;
+	bool capable = true;
+	int ret;
+
+	list_for_each_entry(d, &iommu->domain_list, next) {
+		list_for_each_entry(g, &d->group_list, next) {
+			ret = iommu_group_for_each_dev(g->iommu_group, &capable,
+					vfio_is_dirty_pages_reporting_capable);
+			if (ret)
+				return false;
+		}
+	}
+
+	return capable;
+}
+
 /*
  * start_iova is the reference from where bitmaping started. This is called
  * from DMA_UNMAP where start_iova can be different than iova
@@ -903,10 +936,17 @@ static void vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
 	struct vfio_dma *dma;
 	dma_addr_t i = iova;
 	unsigned long pgshift = __ffs(pgsize);
+	bool dirty_report_cap = true;
+
+	if (IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu))
+		dirty_report_cap = vfio_dirty_pages_reporting_capable(iommu);
 
 	while ((dma = vfio_find_dma(iommu, i, pgsize))) {
-		/* mark all pages dirty if all pages are pinned and mapped. */
-		if (dma->iommu_mapped) {
+		/*
+		 * mark all pages dirty if any IOMMU capable device is not able
+		 * to report dirty pages and all pages are pinned and mapped.
+		 */
+		if (!dirty_report_cap && dma->iommu_mapped) {
 			dma_addr_t iova_limit;
 
 			iova_limit = (dma->iova + dma->size) < (iova + size) ?
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index e42a711a2800..ed3832ea10a1 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -148,7 +148,8 @@ extern int vfio_info_add_capability(struct vfio_info_cap *caps,
 extern int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr,
 					      int num_irqs, int max_irq_type,
 					      size_t *data_size);
-
+extern int vfio_device_is_dirty_reporting_capable(struct device *dev,
+						  bool *cap);
 struct pci_dev;
 #if IS_ENABLED(CONFIG_VFIO_SPAPR_EEH)
 extern void vfio_spapr_pci_eeh_open(struct pci_dev *pdev);
-- 
2.7.0