Re: [PATCH v2 07/20] vfio/common: Add VFIOBitmap and (de)alloc functions

["Cédric Le Goater" <clg@redhat.com>]

On 2/22/23 18:49, Avihai Horon 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 ac93b85632..84f08bdbbb 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -320,6 +320,41 @@ 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);

I think using g_malloc0() for the VFIOBitmap should be fine. If QEMU can
not allocate a couple of bytes, we are in trouble anyway.

Thanks,

C.


> +    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;
> @@ -470,9 +505,14 @@ 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);
> @@ -486,35 +526,28 @@ 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);
>           ret = -E2BIG;
>           goto unmap_exit;
>       }
>   
> -    bitmap->data = g_try_malloc0(bitmap->size);
> -    if (!bitmap->data) {
> -        ret = -ENOMEM;
> -        goto unmap_exit;
> -    }
> -
>       ret = ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, unmap);
>       if (!ret) {
> -        cpu_physical_memory_set_dirty_lebitmap((unsigned long *)bitmap->data,
> -                iotlb->translated_addr, pages);
> +        cpu_physical_memory_set_dirty_lebitmap(vbmap->bitmap,
> +                iotlb->translated_addr, vbmap->pages);
>       } else {
>           error_report("VFIO_UNMAP_DMA with DIRTY_BITMAP : %m");
>       }
>   
> -    g_free(bitmap->data);
>   unmap_exit:
>       g_free(unmap);
> +    vfio_bitmap_dealloc(vbmap);
> +
>       return ret;
>   }
>   
> @@ -1331,7 +1364,7 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
>   {
>       struct vfio_iommu_type1_dirty_bitmap *dbitmap;
>       struct vfio_iommu_type1_dirty_bitmap_get *range;
> -    uint64_t pages;
> +    VFIOBitmap *vbmap;
>       int ret;
>   
>       if (!container->dirty_pages_supported) {
> @@ -1341,6 +1374,11 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
>           return 0;
>       }
>   
> +    vbmap = vfio_bitmap_alloc(size);
> +    if (!vbmap) {
> +        return -errno;
> +    }
> +
>       dbitmap = g_malloc0(sizeof(*dbitmap) + sizeof(*range));
>   
>       dbitmap->argsz = sizeof(*dbitmap) + sizeof(*range);
> @@ -1355,15 +1393,8 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
>        * to qemu_real_host_page_size.
>        */
>       range->bitmap.pgsize = qemu_real_host_page_size();
> -
> -    pages = REAL_HOST_PAGE_ALIGN(range->size) / qemu_real_host_page_size();
> -    range->bitmap.size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) /
> -                                         BITS_PER_BYTE;
> -    range->bitmap.data = g_try_malloc0(range->bitmap.size);
> -    if (!range->bitmap.data) {
> -        ret = -ENOMEM;
> -        goto err_out;
> -    }
> +    range->bitmap.size = vbmap->size;
> +    range->bitmap.data = (__u64 *)vbmap->bitmap;
>   
>       ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap);
>       if (ret) {
> @@ -1374,14 +1405,14 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
>           goto err_out;
>       }
>   
> -    cpu_physical_memory_set_dirty_lebitmap((unsigned long *)range->bitmap.data,
> -                                            ram_addr, pages);
> +    cpu_physical_memory_set_dirty_lebitmap(vbmap->bitmap, ram_addr,
> +                                           vbmap->pages);
>   
>       trace_vfio_get_dirty_bitmap(container->fd, range->iova, range->size,
>                                   range->bitmap.size, ram_addr);
>   err_out:
> -    g_free(range->bitmap.data);
>       g_free(dbitmap);
> +    vfio_bitmap_dealloc(vbmap);
>   
>       return ret;
>   }