rework DMA callbacks (#396)

This fixes a number of issues with how DMA is handled, based on some changes by
Thanos Makatos:

- rename callbacks to register/unregister, as there is not necessarily
any mapping
- provide the (large) page-aligned mapped start and size, the page size used,
as well as the protection flags: some API users need these
- for convenience, provide the virtual address separately that corresponds to
the mapped region
- we should only require a DMA controller to use vfu_addr_to_sg(),
not an unregister callback
- the callbacks should return errno not -errno
- region removal was incorrectly updating the region array
- various other cleanups and clarifications

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

1 files changed, 7 insertions, 14 deletions

diff --git a/samples/gpio-pci-idio-16.c b/samples/gpio-pci-idio-16.c
index 26ac62a..1efc291 100644
--- a/samples/gpio-pci-idio-16.c
+++ b/samples/gpio-pci-idio-16.c
@@ -126,13 +126,12 @@ migration_write_data(UNUSED vfu_ctx_t *vfu_ctx, void *buf, __u64 size,
 }
 
 static void
-map_dma(vfu_ctx_t *vfu_ctx UNUSED, uint64_t iova UNUSED, uint64_t len UNUSED,
-        uint32_t prot UNUSED)
+dma_register(UNUSED vfu_ctx_t *vfu_ctx, UNUSED vfu_dma_info_t *info)
 {
 }
 
 static int
-unmap_dma(vfu_ctx_t *vfu_ctx UNUSED, uint64_t iova UNUSED, uint64_t len UNUSED)
+dma_unregister(UNUSED vfu_ctx_t *vfu_ctx, UNUSED vfu_dma_info_t *info)
 {
     return 0;
 }
@@ -142,7 +141,6 @@ main(int argc, char *argv[])
 {
     int ret;
     bool verbose = false;
-    bool dma = false;
     char opt;
     struct sigaction act = { .sa_handler = _sa_handler };
     vfu_ctx_t *vfu_ctx;
@@ -159,16 +157,13 @@ main(int argc, char *argv[])
         .write_data = &migration_write_data
     };
 
-    while ((opt = getopt(argc, argv, "vd")) != -1) {
+    while ((opt = getopt(argc, argv, "v")) != -1) {
         switch (opt) {
             case 'v':
                 verbose = true;
                 break;
-            case 'd':
-                dma = true;
-                break;
             default: /* '?' */
-                fprintf(stderr, "Usage: %s [-d] [-v] <socketpath>\n", argv[0]);
+                fprintf(stderr, "Usage: %s [-v] <socketpath>\n", argv[0]);
                 exit(EXIT_FAILURE);
         }
     }
@@ -227,11 +222,9 @@ main(int argc, char *argv[])
         err(EXIT_FAILURE, "failed to setup irq counts");
     }
 
-    if (dma) {
-        ret = vfu_setup_device_dma_cb(vfu_ctx, map_dma, unmap_dma);
-        if (ret < 0) {
-            err(EXIT_FAILURE, "failed to setup DMA");
-        }
+    ret = vfu_setup_device_dma(vfu_ctx, dma_register, dma_unregister);
+    if (ret < 0) {
+        err(EXIT_FAILURE, "failed to setup DMA");
     }
 
     ret = vfu_realize_ctx(vfu_ctx);