[Qemu-devel] [RFC v4 7/8] hw: vfio: common: vfio_prepare_msi_mapping

[Eric Auger <eric.auger@redhat.com>]

Introduce an helper function to retrieve the iommu type1 capability
chain info.

The first capability ready to be exploited is the msi geometry
capability. vfio_prepare_msi_mapping allocates a MemoryRegion
dedicated to host MSI IOVA mapping. Its size matches the host needs.
This region is mapped on guest side on the platform bus memory container.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---
v3 -> v4:
- initialize err to NULL

v3: creation
---
 hw/vfio/common.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index fe8a855..c773332 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -34,6 +34,8 @@
 #include "qemu/range.h"
 #include "sysemu/kvm.h"
 #include "trace.h"
+#include "hw/platform-bus.h"
+#include "qapi/error.h"
 
 struct vfio_group_head vfio_group_list =
     QLIST_HEAD_INITIALIZER(vfio_group_list);
@@ -948,12 +950,76 @@ retry:
     return 0;
 }
 
+static struct vfio_info_cap_header *
+vfio_get_iommu_type1_info_cap(struct vfio_iommu_type1_info *info, uint16_t id)
+{
+    struct vfio_info_cap_header *hdr;
+    void *ptr = info;
+
+    if (!(info->flags & VFIO_IOMMU_INFO_CAPS)) {
+        return NULL;
+    }
+
+    for (hdr = ptr + info->cap_offset; hdr != ptr; hdr = ptr + hdr->next) {
+        if (hdr->id == id) {
+            return hdr;
+        }
+    }
+    return NULL;
+}
+
+static void vfio_prepare_msi_mapping(struct vfio_iommu_type1_info *info,
+                                     AddressSpace *as, Error **errp)
+{
+    struct vfio_iommu_type1_info_cap_msi_geometry *msi_geometry;
+    MemoryRegion *pbus_region, *reserved_reg;
+    struct vfio_info_cap_header *hdr;
+    PlatformBusDevice *pbus;
+
+    hdr = vfio_get_iommu_type1_info_cap(info,
+                                        VFIO_IOMMU_TYPE1_INFO_CAP_MSI_GEOMETRY);
+    if (!hdr) {
+        return;
+    }
+
+    msi_geometry = container_of(hdr,
+                                struct vfio_iommu_type1_info_cap_msi_geometry,
+                                header);
+
+    if (msi_geometry->flags & VFIO_IOMMU_MSI_GEOMETRY_RESERVED) {
+        return;
+    }
+
+    /*
+     * MSI must be iommu mapped: allocate a GPA region located on the
+     * platform bus that the host will be able to use for MSI IOVA allocation
+     */
+    reserved_reg = memory_region_find_by_name(as->root, "reserved-iova");
+    if (reserved_reg) {
+        memory_region_unref(reserved_reg);
+        return;
+    }
+
+    pbus_region = memory_region_find_by_name(as->root, "platform bus");
+    if (!pbus_region) {
+        error_setg(errp, "no platform bus memory container found");
+        return;
+    }
+    pbus = container_of(pbus_region, PlatformBusDevice, mmio);
+    reserved_reg = g_new0(MemoryRegion, 1);
+    memory_region_init_reserved_iova(reserved_reg, OBJECT(pbus),
+                                     "reserved-iova",
+                                     msi_geometry->size, &error_fatal);
+    platform_bus_map_region(pbus, reserved_reg);
+    memory_region_unref(pbus_region);
+}
 
 static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
 {
     VFIOContainer *container;
     int ret, fd;
     VFIOAddressSpace *space;
+    Error *err = NULL;
 
     space = vfio_get_address_space(as);
 
@@ -1011,6 +1077,14 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
          * going to actually try in practice.
          */
         vfio_get_iommu_type1_info(fd, &pinfo);
+        vfio_prepare_msi_mapping(pinfo, as, &err);
+        if (err) {
+            error_append_hint(&err,
+                    "Make sure your machine instantiates a platform bus\n");
+            error_report_err(err);
+            goto free_container_exit;
+        }
+
         /* Ignore errors */
         if (ret || !(pinfo->flags & VFIO_IOMMU_INFO_PGSIZES)) {
             /* Assume 4k IOVA page size */
-- 
1.9.1