[PULL 09/15] vfio: Query and store the maximum number of possible DMA mappings

[Eduardo Habkost <ehabkost@redhat.com>]

From: David Hildenbrand <david@redhat.com>

Let's query the maximum number of possible DMA mappings by querying the
available mappings when creating the container (before any mappings are
created). We'll use this informaton soon to perform some sanity checks
and warn the user.

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210413095531.25603-8-david@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 include/hw/vfio/vfio-common.h | 1 +
 hw/vfio/common.c              | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 681432213d1..8af11b0a769 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -88,6 +88,7 @@ typedef struct VFIOContainer {
     uint64_t dirty_pgsizes;
     uint64_t max_dirty_bitmap_size;
     unsigned long pgsizes;
+    unsigned int dma_max_mappings;
     QLIST_HEAD(, VFIOGuestIOMMU) giommu_list;
     QLIST_HEAD(, VFIOHostDMAWindow) hostwin_list;
     QLIST_HEAD(, VFIOGroup) group_list;
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5af77552279..79628d60aed 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1931,6 +1931,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
     container->fd = fd;
     container->error = NULL;
     container->dirty_pages_supported = false;
+    container->dma_max_mappings = 0;
     QLIST_INIT(&container->giommu_list);
     QLIST_INIT(&container->hostwin_list);
     QLIST_INIT(&container->vrdl_list);
@@ -1962,7 +1963,10 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
         vfio_host_win_add(container, 0, (hwaddr)-1, info->iova_pgsizes);
         container->pgsizes = info->iova_pgsizes;
 
+        /* The default in the kernel ("dma_entry_limit") is 65535. */
+        container->dma_max_mappings = 65535;
         if (!ret) {
+            vfio_get_info_dma_avail(info, &container->dma_max_mappings);
             vfio_get_iommu_info_migration(container, info);
         }
         g_free(info);
-- 
2.31.1