On Mon, Aug 16, 2021 at 09:42:49AM -0700, Elena Ufimtseva wrote:
> @@ -1356,7 +1365,11 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
>          goto err_out;
>      }
>  
> -    ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap);
> +    if (container->proxy != NULL) {
> +        ret = vfio_user_dirty_bitmap(container->proxy, dbitmap, range);
> +    } else {
> +        ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap);
> +    }
>      if (ret) {
>          error_report("Failed to get dirty bitmap for iova: 0x%"PRIx64
>                  " size: 0x%"PRIx64" err: %d", (uint64_t)range->iova,

This error_report() relies on errno. vfio_user_region_write() doesn't
set errno.

> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 82f654afb6..89926a3b01 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -27,6 +27,7 @@
>  #include "pci.h"
>  #include "trace.h"
>  #include "hw/hw.h"
> +#include "user.h"
>  
>  /*
>   * Flags to be used as unique delimiters for VFIO devices in the migration
> @@ -49,10 +50,18 @@ static int64_t bytes_transferred;
>  static inline int vfio_mig_access(VFIODevice *vbasedev, void *val, int count,
>                                    off_t off, bool iswrite)
>  {
> +    VFIORegion *region = &vbasedev->migration->region;
>      int ret;
>  
> -    ret = iswrite ? pwrite(vbasedev->fd, val, count, off) :
> -                    pread(vbasedev->fd, val, count, off);
> +    if (vbasedev->proxy != NULL) {
> +        ret = iswrite ?
> +            vfio_user_region_write(vbasedev, region->nr, off, count, val) :
> +            vfio_user_region_read(vbasedev, region->nr, off, count, val);
> +    } else {
> +        off += region->fd_offset;
> +        ret = iswrite ? pwrite(vbasedev->fd, val, count, off) :
> +                        pread(vbasedev->fd, val, count, off);
> +    }
>      if (ret < count) {
>          error_report("vfio_mig_%s %d byte %s: failed at offset 0x%"
>                       HWADDR_PRIx", err: %s", iswrite ? "write" : "read", count,

Another errno user. I haven't exhaustively audited all the code for
these issues. Please take a look.