[PATCH v2 1/2] util/vfio-helpers: Collect IOVA reserved regions

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

The IOVA allocator currently ignores host reserved regions.
As a result some chosen IOVAs may collide with some of them,
resulting in VFIO MAP_DMA errors later on. This happens on ARM
where the MSI reserved window quickly is encountered:
[0x8000000, 0x8100000]. since 5.4 kernel, VFIO returns the usable
IOVA regions. So let's enumerate them in the prospect to avoid
them, later on.

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

---

v1 -> v2:
- fix the loop on caps
- set s->usable_iova_ranges=NULL to avoid double free
---
 util/vfio-helpers.c | 72 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 2 deletions(-)

diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index 583bdfb36f..ba0ee6e21c 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -40,6 +40,11 @@ typedef struct {
     uint64_t iova;
 } IOVAMapping;
 
+struct IOVARange {
+    uint64_t start;
+    uint64_t end;
+};
+
 struct QEMUVFIOState {
     QemuMutex lock;
 
@@ -49,6 +54,8 @@ struct QEMUVFIOState {
     int device;
     RAMBlockNotifier ram_notifier;
     struct vfio_region_info config_region_info, bar_region_info[6];
+    struct IOVARange *usable_iova_ranges;
+    uint8_t nb_iova_ranges;
 
     /* These fields are protected by @lock */
     /* VFIO's IO virtual address space is managed by splitting into a few
@@ -236,6 +243,35 @@ static int qemu_vfio_pci_write_config(QEMUVFIOState *s, void *buf, int size, int
     return ret == size ? 0 : -errno;
 }
 
+static void collect_usable_iova_ranges(QEMUVFIOState *s, void *buf)
+{
+    struct vfio_iommu_type1_info *info = (struct vfio_iommu_type1_info *)buf;
+    struct vfio_info_cap_header *cap = (void *)buf + info->cap_offset;
+    struct vfio_iommu_type1_info_cap_iova_range *cap_iova_range;
+    int i;
+
+    while (cap->id != VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE) {
+        if (!cap->next) {
+            return;
+        }
+        cap = (struct vfio_info_cap_header *)(buf + cap->next);
+    }
+
+    cap_iova_range = (struct vfio_iommu_type1_info_cap_iova_range *)cap;
+
+    s->nb_iova_ranges = cap_iova_range->nr_iovas;
+    if (s->nb_iova_ranges > 1) {
+        s->usable_iova_ranges =
+            g_realloc(s->usable_iova_ranges,
+                      s->nb_iova_ranges * sizeof(struct IOVARange));
+    }
+
+    for (i = 0; i < s->nb_iova_ranges; i++) {
+        s->usable_iova_ranges[i].start = cap_iova_range->iova_ranges[i].start;
+        s->usable_iova_ranges[i].end = cap_iova_range->iova_ranges[i].end;
+    }
+}
+
 static int qemu_vfio_init_pci(QEMUVFIOState *s, const char *device,
                               Error **errp)
 {
@@ -243,10 +279,13 @@ static int qemu_vfio_init_pci(QEMUVFIOState *s, const char *device,
     int i;
     uint16_t pci_cmd;
     struct vfio_group_status group_status = { .argsz = sizeof(group_status) };
-    struct vfio_iommu_type1_info iommu_info = { .argsz = sizeof(iommu_info) };
+    struct vfio_iommu_type1_info *iommu_info = NULL;
+    size_t iommu_info_size = sizeof(*iommu_info);
     struct vfio_device_info device_info = { .argsz = sizeof(device_info) };
     char *group_file = NULL;
 
+    s->usable_iova_ranges = NULL;
+
     /* Create a new container */
     s->container = open("/dev/vfio/vfio", O_RDWR);
 
@@ -310,13 +349,35 @@ static int qemu_vfio_init_pci(QEMUVFIOState *s, const char *device,
         goto fail;
     }
 
+    iommu_info = g_malloc0(iommu_info_size);
+    iommu_info->argsz = iommu_info_size;
+
     /* Get additional IOMMU info */
-    if (ioctl(s->container, VFIO_IOMMU_GET_INFO, &iommu_info)) {
+    if (ioctl(s->container, VFIO_IOMMU_GET_INFO, iommu_info)) {
         error_setg_errno(errp, errno, "Failed to get IOMMU info");
         ret = -errno;
         goto fail;
     }
 
+    /*
+     * if the kernel does not report usable IOVA regions, choose
+     * the legacy [QEMU_VFIO_IOVA_MIN, QEMU_VFIO_IOVA_MAX -1] region
+     */
+    s->nb_iova_ranges = 1;
+    s->usable_iova_ranges = g_new0(struct IOVARange, 1);
+    s->usable_iova_ranges[0].start = QEMU_VFIO_IOVA_MIN;
+    s->usable_iova_ranges[0].end = QEMU_VFIO_IOVA_MAX - 1;
+
+    if (iommu_info->argsz > iommu_info_size) {
+        iommu_info_size = iommu_info->argsz;
+        iommu_info = g_realloc(iommu_info, iommu_info_size);
+        if (ioctl(s->container, VFIO_IOMMU_GET_INFO, iommu_info)) {
+            ret = -errno;
+            goto fail;
+        }
+        collect_usable_iova_ranges(s, iommu_info);
+    }
+
     s->device = ioctl(s->group, VFIO_GROUP_GET_DEVICE_FD, device);
 
     if (s->device < 0) {
@@ -365,8 +426,13 @@ static int qemu_vfio_init_pci(QEMUVFIOState *s, const char *device,
     if (ret) {
         goto fail;
     }
+    g_free(iommu_info);
     return 0;
 fail:
+    g_free(s->usable_iova_ranges);
+    s->usable_iova_ranges = NULL;
+    s->nb_iova_ranges = 0;
+    g_free(iommu_info);
     close(s->group);
 fail_container:
     close(s->container);
@@ -716,6 +782,8 @@ void qemu_vfio_close(QEMUVFIOState *s)
         qemu_vfio_undo_mapping(s, &s->mappings[i], NULL);
     }
     ram_block_notifier_remove(&s->ram_notifier);
+    g_free(s->usable_iova_ranges);
+    s->nb_iova_ranges = 0;
     qemu_vfio_reset(s);
     close(s->device);
     close(s->group);
-- 
2.21.3