[PATCH v2 14/19] util/vfio-helpers: Pass minimum page size to qemu_vfio_open_pci()

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

The block driver asks for a minimum page size, but it might not
match the minimum IOMMU requirement.

In the next commit qemu_vfio_init_pci() will be able to report
the minimum IOMMU page size back to the block driver.
In preparation, pass the minimum page size as argument to
qemu_vfio_open_pci(). Add a check to be sure the IOMMU minimum
page size is in range with our NVMe device maximum page size.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/qemu/vfio-helpers.h |  3 ++-
 block/nvme.c                | 14 +++++++++++++-
 util/vfio-helpers.c         |  8 +++++++-
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/qemu/vfio-helpers.h b/include/qemu/vfio-helpers.h
index bde9495b254..4b97a904e93 100644
--- a/include/qemu/vfio-helpers.h
+++ b/include/qemu/vfio-helpers.h
@@ -15,7 +15,8 @@
 
 typedef struct QEMUVFIOState QEMUVFIOState;
 
-QEMUVFIOState *qemu_vfio_open_pci(const char *device, Error **errp);
+QEMUVFIOState *qemu_vfio_open_pci(const char *device, size_t *min_page_size,
+                                  Error **errp);
 void qemu_vfio_close(QEMUVFIOState *s);
 int qemu_vfio_dma_map(QEMUVFIOState *s, void *host, size_t size,
                       bool temporary, uint64_t *iova_list, Error **errp);
diff --git a/block/nvme.c b/block/nvme.c
index 6f1ebdf031f..46b09b3a3a7 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -691,6 +691,7 @@ static int nvme_init(BlockDriverState *bs, const char *device, int namespace,
     Error *local_err = NULL;
     volatile NvmeBar *regs = NULL;
     size_t device_page_size_min;
+    size_t device_page_size_max;
     size_t iommu_page_size_min = 4096;
 
     qemu_co_mutex_init(&s->dma_map_lock);
@@ -704,7 +705,7 @@ static int nvme_init(BlockDriverState *bs, const char *device, int namespace,
         return ret;
     }
 
-    s->vfio = qemu_vfio_open_pci(device, errp);
+    s->vfio = qemu_vfio_open_pci(device, &iommu_page_size_min, errp);
     if (!s->vfio) {
         ret = -EINVAL;
         goto out;
@@ -737,6 +738,17 @@ static int nvme_init(BlockDriverState *bs, const char *device, int namespace,
     }
 
     device_page_size_min = 1u << (12 + NVME_CAP_MPSMIN(cap));
+    device_page_size_max = 1u << (12 + NVME_CAP_MPSMAX(cap));
+    if (iommu_page_size_min > device_page_size_max) {
+        g_autofree char *iommu_page_size_s = size_to_str(iommu_page_size_min);
+        g_autofree char *device_page_size_s = size_to_str(device_page_size_max);
+
+        error_setg(errp, "IOMMU minimum page size (%s)"
+                         " too big for device (max %s)",
+                   iommu_page_size_s, device_page_size_s);
+        ret = -EINVAL;
+        goto out;
+    }
     s->page_size = MAX(iommu_page_size_min, device_page_size_min);
     s->doorbell_scale = (4 << NVME_CAP_DSTRD(cap)) / sizeof(uint32_t);
     bs->bl.opt_mem_alignment = s->page_size;
diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index 488ddfca2a9..5e288dfa113 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -508,8 +508,14 @@ static void qemu_vfio_open_common(QEMUVFIOState *s)
 
 /**
  * Open a PCI device, e.g. "0000:00:01.0".
+ *
+ * @min_page_size: Pointer holding the minimum page size requested
+ *
+ * If the IOMMU can not be configured with @min_page_size, the minimum
+ * page size is stored in @min_page_size and -EINVAL is returned.
  */
-QEMUVFIOState *qemu_vfio_open_pci(const char *device, Error **errp)
+QEMUVFIOState *qemu_vfio_open_pci(const char *device, size_t *min_page_size,
+                                  Error **errp)
 {
     int r;
     QEMUVFIOState *s = g_new0(QEMUVFIOState, 1);
-- 
2.26.2