migration: various dirty page tracking fixes (#457)

- document how to use a vfio-user device with libvirt
- document how to use SPDK's nvmf/vfio-user target with libvirt
- replace vfio_bitmap with vfio_user_bitmap and vfio_iommu_type1_dirty_bitmap_get with vfio_user_bitmap_range
- fix bug for calculating number of pages needed for dirty page bitmap
- align number of bytes for dirty page bitmap to QWORD
- add debug messages around dirty page tracking
- only support flags=0 when doing DMA unmap
- set device state to running after reset
- allow region read/write even if device is in stopped state
- allow transitioning from stopped/stop-and-copy state to running state
- fix unit tests

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

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/dma.c b/lib/dma.c
index 32f786b..e6d04b3 100644
--- a/lib/dma.c
+++ b/lib/dma.c
@@ -423,7 +423,7 @@ get_bitmap_size(size_t region_size, size_t pgsize)
         return ERROR_INT(EINVAL);
     }
     size_t nr_pages = (region_size / pgsize) + (region_size % pgsize != 0);
-    return (nr_pages / CHAR_BIT) + (nr_pages % CHAR_BIT != 0);
+    return ROUND_UP(nr_pages, sizeof(uint64_t) * CHAR_BIT) / CHAR_BIT;
 }
 
 int dma_controller_dirty_page_logging_start(dma_controller_t *dma, size_t pgsize)
@@ -511,11 +511,13 @@ dma_controller_dirty_page_get(dma_controller_t *dma, vfu_dma_addr_t addr,
     }
 
     if (pgsize != dma->dirty_pgsize) {
+        vfu_log(dma->vfu_ctx, LOG_ERR, "bad page size %ld", pgsize);
         return ERROR_INT(EINVAL);
     }
 
     bitmap_size = get_bitmap_size(len, pgsize);
     if (bitmap_size < 0) {
+        vfu_log(dma->vfu_ctx, LOG_ERR, "failed to get bitmap size");
         return bitmap_size;
     }
 
@@ -524,6 +526,8 @@ dma_controller_dirty_page_get(dma_controller_t *dma, vfu_dma_addr_t addr,
      * expects to receive.
      */
     if (size != (size_t)bitmap_size) {
+        vfu_log(dma->vfu_ctx, LOG_ERR, "bad bitmap size %ld != %ld", size,
+                bitmap_size);
         return ERROR_INT(EINVAL);
     }