vfu_realize_ctx(): fix default PCI config space region (#445)

Fix check for an un-configured PCI config space region (the previous method was
not accounting for the initialized ->fd).

Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@nutanix.com>

2 files changed, 17 insertions, 7 deletions

diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index a0f6fe3..82fe0ca 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -1013,7 +1013,6 @@ int
 vfu_realize_ctx(vfu_ctx_t *vfu_ctx)
 {
     vfu_reg_info_t *cfg_reg;
-    const vfu_reg_info_t zero_reg = { 0 };
     uint32_t max_ivs = 0, i;
     size_t size;
 
@@ -1024,8 +1023,7 @@ vfu_realize_ctx(vfu_ctx_t *vfu_ctx)
     cfg_reg = &vfu_ctx->reg_info[VFU_PCI_DEV_CFG_REGION_IDX];
 
     // Set a default config region if none provided.
-    /* TODO should it be enough to check that the size of region is 0? */
-    if (memcmp(cfg_reg, &zero_reg, sizeof(*cfg_reg)) == 0) {
+    if (cfg_reg->size == 0) {
         cfg_reg->flags = VFU_REGION_FLAG_RW;
         cfg_reg->size = PCI_CFG_SPACE_SIZE;
     }
@@ -1227,6 +1225,10 @@ vfu_create_ctx(vfu_trans_t trans, const char *path, int flags, void *pvt,
         goto err_out;
     }
 
+    for (i = 0; i < vfu_ctx->nr_regions; i++) {
+        vfu_ctx->reg_info[i].fd = -1;
+    }
+
     if (vfu_setup_device_nr_irqs(vfu_ctx, VFU_DEV_ERR_IRQ, 1) == -1) {
         goto err_out;
     }
@@ -1241,10 +1243,6 @@ vfu_create_ctx(vfu_trans_t trans, const char *path, int flags, void *pvt,
         }
     }
 
-    for (i = 0; i< vfu_ctx->nr_regions; i++) {
-        vfu_ctx->reg_info[i].fd = -1;
-    }
-
     return vfu_ctx;
 
 err_out:
diff --git a/test/unit-tests.c b/test/unit-tests.c
index 7f03fb7..9aa1106 100644
--- a/test/unit-tests.c
+++ b/test/unit-tests.c
@@ -737,6 +737,18 @@ test_vfu_ctx_create(void **state UNUSED)
     will_return(close, 0);
 
     vfu_destroy_ctx(vfu_ctx);
+
+    /* Test "bare" vfu_create_ctx(). */
+    vfu_ctx = vfu_create_ctx(VFU_TRANS_SOCK, "", LIBVFIO_USER_FLAG_ATTACH_NB,
+                             NULL, VFU_DEV_TYPE_PCI);
+    assert_non_null(vfu_ctx);
+
+    assert_int_equal(0, vfu_realize_ctx(vfu_ctx));
+
+    expect_value(close, fd, ((tran_sock_t *)vfu_ctx->tran_data)->fd);
+    will_return(close, 0);
+
+    vfu_destroy_ctx(vfu_ctx);
 }
 
 bool pci_caps_writing = true;