adapt to VFIO live migration v2 (#782)

This commit adapts the vfio-user protocol specification and the libvfio-user
implementation to v2 of the VFIO live migration interface, as used in the kernel
and QEMU.

The differences between v1 and v2 are discussed in this email thread [1], and we
slightly differ from upstream VFIO v2 in that instead of transferring data over
a new FD, we use the existing UNIX socket with new commands
VFIO_USER_MIG_DATA_READ/WRITE. We also don't yet use P2P states.

The updated spec was submitted to qemu-devel [2].

[1] https://lore.kernel.org/all/20220130160826.32449-9-yishaih@nvidia.com/
[2] https://lore.kernel.org/all/20230718094150.110183-1-william.henderson@nutanix.com/

Signed-off-by: William Henderson <william.henderson@nutanix.com>

1 files changed, 8 insertions, 46 deletions

diff --git a/samples/gpio-pci-idio-16.c b/samples/gpio-pci-idio-16.c
index b50f407..6c4e99b 100644
--- a/samples/gpio-pci-idio-16.c
+++ b/samples/gpio-pci-idio-16.c
@@ -77,49 +77,23 @@ migration_device_state_transition(vfu_ctx_t *vfu_ctx, vfu_migr_state_t state)
     return 0;
 }
 
-static uint64_t
-migration_get_pending_bytes(UNUSED vfu_ctx_t *vfu_ctx)
+static ssize_t
+migration_read_data(UNUSED vfu_ctx_t *vfu_ctx, void *buf, uint64_t size)
 {
+    assert(size == sizeof(pin));
+
     if (dirty) {
+        memcpy(buf, &pin, sizeof(pin));
+        dirty = false;
         return sizeof(pin);
     }
-    return 0;
-}
 
-static int
-migration_prepare_data(UNUSED vfu_ctx_t *vfu_ctx,
-                       uint64_t *offset, uint64_t *size)
-{
-    *offset = 0;
-    if (size != NULL) { /* null means resuming */
-        *size = sizeof(pin);
-    }
     return 0;
 }
 
 static ssize_t
-migration_read_data(UNUSED vfu_ctx_t *vfu_ctx, void *buf,
-                    uint64_t size, uint64_t offset)
+migration_write_data(UNUSED vfu_ctx_t *vfu_ctx, void *buf, uint64_t size)
 {
-    assert(offset == 0);
-    assert(size == sizeof(pin));
-    memcpy(buf, &pin, sizeof(pin));
-    dirty = false;
-    return 0;
-}
-
-static int
-migration_data_written(UNUSED vfu_ctx_t *vfu_ctx, uint64_t count)
-{
-    assert(count == sizeof(pin));
-    return 0;
-}
-
-static ssize_t
-migration_write_data(UNUSED vfu_ctx_t *vfu_ctx, void *buf,
-                     uint64_t size, uint64_t offset)
-{
-    assert(offset == 0);
     assert(size == sizeof(pin));
     memcpy(&pin, buf, sizeof(pin));
     return 0;
@@ -145,16 +119,10 @@ main(int argc, char *argv[])
     int opt;
     struct sigaction act = { .sa_handler = _sa_handler };
     vfu_ctx_t *vfu_ctx;
-    size_t migr_regs_size = vfu_get_migr_register_area_size();
-    size_t migr_data_size = sysconf(_SC_PAGE_SIZE);
-    size_t migr_size = migr_regs_size + migr_data_size;
     const vfu_migration_callbacks_t migr_callbacks = {
         .version = VFU_MIGR_CALLBACKS_VERS,
         .transition = &migration_device_state_transition,
-        .get_pending_bytes = &migration_get_pending_bytes,
-        .prepare_data = &migration_prepare_data,
         .read_data = &migration_read_data,
-        .data_written = &migration_data_written,
         .write_data = &migration_write_data
     };
 
@@ -214,13 +182,7 @@ main(int argc, char *argv[])
     }
 
     if (enable_migr) {
-        ret = vfu_setup_region(vfu_ctx, VFU_PCI_DEV_MIGR_REGION_IDX, migr_size,
-                               NULL, VFU_REGION_FLAG_RW, NULL, 0, -1, 0);
-        if (ret < 0) {
-            err(EXIT_FAILURE, "failed to setup migration region");
-        }
-        ret = vfu_setup_device_migration_callbacks(vfu_ctx, &migr_callbacks,
-                                                   migr_regs_size);
+        ret = vfu_setup_device_migration_callbacks(vfu_ctx, &migr_callbacks);
         if (ret < 0) {
             err(EXIT_FAILURE, "failed to setup device migration");
         }