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

[Alex Williamson]

On Sun, 12 Feb 2023 17:36:49 +0200
Avihai Horon <avihaih@nvidia.com> wrote:

> On 27/01/2023 23:11, Alex Williamson wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > 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?  
> 
> Hi, sorry for the delay.
> 
> This test is relevant only for VFIO IOMMU dirty tracking. With device 
> dirty tracking it should be skipped.
> Do you think we should still move it to the alloc function?

Ah, ok.  Sounds like we'll have to live with a separate test for the
container path.  Thanks,

Alex