virtio-iommu: Set supported page size mask

The virtio-iommu device can deal with arbitrary page sizes for virtual
endpoints, but for endpoints assigned with VFIO it must follow the page
granule used by the host IOMMU driver.

Implement the interface to set the vIOMMU page size mask, called by VFIO
for each endpoint. We assume that all host IOMMU drivers use the same
page granule (the host page granule). Override the page_size_mask field
in the virtio config space.

Signed-off-by: Bharat Bhushan <bbhushan2@marvell.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-Id: <20201030180510.747225-10-jean-philippe@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index 78e07aa40a..fc5c75d693 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -899,6 +899,55 @@ static int virtio_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu_mr,
     return 0;
 }
 
+/*
+ * The default mask (TARGET_PAGE_MASK) is the smallest supported guest granule,
+ * for example 0xfffffffffffff000. When an assigned device has page size
+ * restrictions due to the hardware IOMMU configuration, apply this restriction
+ * to the mask.
+ */
+static int virtio_iommu_set_page_size_mask(IOMMUMemoryRegion *mr,
+                                           uint64_t new_mask,
+                                           Error **errp)
+{
+    IOMMUDevice *sdev = container_of(mr, IOMMUDevice, iommu_mr);
+    VirtIOIOMMU *s = sdev->viommu;
+    uint64_t cur_mask = s->config.page_size_mask;
+
+    trace_virtio_iommu_set_page_size_mask(mr->parent_obj.name, cur_mask,
+                                          new_mask);
+
+    if ((cur_mask & new_mask) == 0) {
+        error_setg(errp, "virtio-iommu page mask 0x%"PRIx64
+                   " is incompatible with mask 0x%"PRIx64, cur_mask, new_mask);
+        return -1;
+    }
+
+    /*
+     * After the machine is finalized, we can't change the mask anymore. If by
+     * chance the hotplugged device supports the same granule, we can still
+     * accept it. Having a different masks is possible but the guest will use
+     * sub-optimal block sizes, so warn about it.
+     */
+    if (qdev_hotplug) {
+        int new_granule = ctz64(new_mask);
+        int cur_granule = ctz64(cur_mask);
+
+        if (new_granule != cur_granule) {
+            error_setg(errp, "virtio-iommu page mask 0x%"PRIx64
+                       " is incompatible with mask 0x%"PRIx64, cur_mask,
+                       new_mask);
+            return -1;
+        } else if (new_mask != cur_mask) {
+            warn_report("virtio-iommu page mask 0x%"PRIx64
+                        " does not match 0x%"PRIx64, cur_mask, new_mask);
+        }
+        return 0;
+    }
+
+    s->config.page_size_mask &= new_mask;
+    return 0;
+}
+
 static void virtio_iommu_device_realize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
@@ -1130,6 +1179,7 @@ static void virtio_iommu_memory_region_class_init(ObjectClass *klass,
     imrc->translate = virtio_iommu_translate;
     imrc->replay = virtio_iommu_replay;
     imrc->notify_flag_changed = virtio_iommu_notify_flag_changed;
+    imrc->iommu_set_page_size_mask = virtio_iommu_set_page_size_mask;
 }
 
 static const TypeInfo virtio_iommu_info = {