When vIOMMU is enabled, syncing dirty page bitmaps is done by replaying
the vIOMMU mappings and querying the dirty bitmap for each mapping.
With device dirty tracking this causes a lot of overhead, since the HW
is queried many times (even with small idle guest this can end up with
thousands of calls to HW).
Optimize this by de-coupling dirty bitmap query from vIOMMU replay.
Now a single dirty bitmap is queried per vIOMMU MR section, which is
then used for all corresponding vIOMMU mappings within that MR section.
Signed-off-by: Avihai Horon <avih...@nvidia.com>
---
hw/vfio/common.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 83 insertions(+), 2 deletions(-)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 1024788bcc..f16a57d42b 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1946,8 +1946,42 @@ out:
typedef struct {
IOMMUNotifier n;
VFIOGuestIOMMU *giommu;
+ VFIOBitmap *vbmap;
} vfio_giommu_dirty_notifier;
+static int vfio_iommu_set_dirty_bitmap(VFIOContainer *container,
+ vfio_giommu_dirty_notifier *gdn,
+ hwaddr iova, hwaddr size,
+ ram_addr_t ram_addr)
+{
+ VFIOBitmap *vbmap = gdn->vbmap;
+ VFIOBitmap *dst_vbmap;
+ hwaddr start_iova = REAL_HOST_PAGE_ALIGN(gdn->n.start);
+ hwaddr copy_offset;
+
+ dst_vbmap = vfio_bitmap_alloc(size);
+ if (!dst_vbmap) {
+ return -errno;
+ }
+
+ if (!vfio_iommu_range_is_device_tracked(container, iova, size)) {
+ bitmap_set(dst_vbmap->bitmap, 0, dst_vbmap->pages);
+
+ goto out;
+ }
+
+ copy_offset = (iova - start_iova) / qemu_real_host_page_size();
+ bitmap_copy_with_src_offset(dst_vbmap->bitmap, vbmap->bitmap, copy_offset,
+ dst_vbmap->pages);
+
+out:
+ cpu_physical_memory_set_dirty_lebitmap(dst_vbmap->bitmap, ram_addr,
+ dst_vbmap->pages);
+ vfio_bitmap_dealloc(dst_vbmap);
+
+ return 0;
+}
+
static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
{
vfio_giommu_dirty_notifier *gdn = container_of(n,
@@ -1968,8 +2002,15 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier
*n, IOMMUTLBEntry *iotlb)
rcu_read_lock();
if (vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL)) {
- ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1,
- translated_addr);
+ if (gdn->vbmap) {
+ ret = vfio_iommu_set_dirty_bitmap(container, gdn, iova,
+ iotlb->addr_mask + 1,
+ translated_addr);
+ } else {
+ ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1,
+ translated_addr);
+ }
+
if (ret) {
error_report("vfio_iommu_map_dirty_notify(%p, 0x%"HWADDR_PRIx", "
"0x%"HWADDR_PRIx") = %d (%s)",
@@ -2033,6 +2074,7 @@ static int vfio_sync_iommu_dirty_bitmap(VFIOContainer
*container,
{
VFIOGuestIOMMU *giommu;
bool found = false;
+ VFIOBitmap *vbmap = NULL;
Int128 llend;
vfio_giommu_dirty_notifier gdn;
int idx;
@@ -2050,6 +2092,7 @@ static int vfio_sync_iommu_dirty_bitmap(VFIOContainer
*container,
}
gdn.giommu = giommu;
+ gdn.vbmap = NULL;
idx = memory_region_iommu_attrs_to_index(giommu->iommu_mr,
MEMTXATTRS_UNSPECIFIED);
@@ -2057,11 +2100,49 @@ static int vfio_sync_iommu_dirty_bitmap(VFIOContainer
*container,
section->size);
llend = int128_sub(llend, int128_one());
+ /*
+ * Optimize device dirty tracking if the MR section is at least partially
+ * tracked. Optimization is done by querying a single dirty bitmap for the
+ * entire range instead of querying dirty bitmap for each vIOMMU mapping.
+ */
+ if (vfio_devices_all_device_dirty_tracking(container)) {
+ hwaddr start = REAL_HOST_PAGE_ALIGN(section->offset_within_region);
+ hwaddr end = int128_get64(llend);
+ hwaddr size;
+ int ret;
+
+ if (start >= container->giommu_tracked_range) {
+ goto notifier_init;
+ }
+
+ size = REAL_HOST_PAGE_ALIGN(
+ MIN(container->giommu_tracked_range - 1, end) - start);
+
+ vbmap = vfio_bitmap_alloc(size);
+ if (!vbmap) {
+ return -errno;
+ }
+
+ ret = vfio_devices_query_dirty_bitmap(container, vbmap, start, size);
+ if (ret) {
+ vfio_bitmap_dealloc(vbmap);
+
+ return ret;
+ }
+
+ gdn.vbmap = vbmap;
+ }
+
+notifier_init:
iommu_notifier_init(&gdn.n, vfio_iommu_map_dirty_notify,
IOMMU_NOTIFIER_MAP,
section->offset_within_region, int128_get64(llend),
idx);
memory_region_iommu_replay(giommu->iommu_mr, &gdn.n);
+ if (vbmap) {
+ vfio_bitmap_dealloc(vbmap);
+ }
+
return 0;
}
--
2.26.3
