Re: [PATCH 05/18] vfio/common: Add VFIOBitmap and (de)alloc functions

[Alex Williamson]

On Thu, 26 Jan 2023 20:49:35 +0200
Avihai Horon <avihaih@nvidia.com> wrote:

> There are already two places where dirty page bitmap allocation and
> calculations are done in open code. With device dirty page tracking
> being added in next patches, there are going to be even more places.
> 
> To avoid code duplication, introduce VFIOBitmap struct and corresponding
> alloc and dealloc functions and use them where applicable.
> 
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> ---
>  hw/vfio/common.c | 89 ++++++++++++++++++++++++++++++++----------------
>  1 file changed, 60 insertions(+), 29 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 8e8ffbc046..e554573eb5 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -319,6 +319,41 @@ const MemoryRegionOps vfio_region_ops = {
>   * Device state interfaces
>   */
>  
> +typedef struct {
> +    unsigned long *bitmap;
> +    hwaddr size;
> +    hwaddr pages;
> +} VFIOBitmap;
> +
> +static VFIOBitmap *vfio_bitmap_alloc(hwaddr size)
> +{
> +    VFIOBitmap *vbmap = g_try_new0(VFIOBitmap, 1);
> +    if (!vbmap) {
> +        errno = ENOMEM;
> +
> +        return NULL;
> +    }
> +
> +    vbmap->pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size();
> +    vbmap->size =  ROUND_UP(vbmap->pages, sizeof(__u64) * BITS_PER_BYTE) /
> +                                          BITS_PER_BYTE;
> +    vbmap->bitmap = g_try_malloc0(vbmap->size);
> +    if (!vbmap->bitmap) {
> +        g_free(vbmap);
> +        errno = ENOMEM;
> +
> +        return NULL;
> +    }
> +
> +    return vbmap;
> +}
> +
> +static void vfio_bitmap_dealloc(VFIOBitmap *vbmap)
> +{
> +    g_free(vbmap->bitmap);
> +    g_free(vbmap);
> +}
> +
>  bool vfio_mig_active(void)
>  {
>      VFIOGroup *group;
> @@ -421,9 +456,14 @@ static int vfio_dma_unmap_bitmap(VFIOContainer 
> *container,
>  {
>      struct vfio_iommu_type1_dma_unmap *unmap;
>      struct vfio_bitmap *bitmap;
> -    uint64_t pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size();
> +    VFIOBitmap *vbmap;
>      int ret;
>  
> +    vbmap = vfio_bitmap_alloc(size);
> +    if (!vbmap) {
> +        return -errno;
> +    }
> +
>      unmap = g_malloc0(sizeof(*unmap) + sizeof(*bitmap));
>  
>      unmap->argsz = sizeof(*unmap) + sizeof(*bitmap);
> @@ -437,35 +477,28 @@ static int vfio_dma_unmap_bitmap(VFIOContainer 
> *container,
>       * qemu_real_host_page_size to mark those dirty. Hence set bitmap_pgsize
>       * to qemu_real_host_page_size.
>       */
> -
>      bitmap->pgsize = qemu_real_host_page_size();
> -    bitmap->size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) /
> -                   BITS_PER_BYTE;
> +    bitmap->size = vbmap->size;
> +    bitmap->data = (__u64 *)vbmap->bitmap;
>  
> -    if (bitmap->size > container->max_dirty_bitmap_size) {
> -        error_report("UNMAP: Size of bitmap too big 0x%"PRIx64,
> -                     (uint64_t)bitmap->size);
> +    if (vbmap->size > container->max_dirty_bitmap_size) {
> +        error_report("UNMAP: Size of bitmap too big 0x%"PRIx64, vbmap->size);

Why not pass the container to the alloc function so we can test this
consistently for each bitmap we allocate?  Thanks,

Alex