Re: [PATCH] vfio: Support host translation granule size

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 4 Mar 2021 21:34:46 +0800
Kunkun Jiang <jiangkunkun@huawei.com> wrote:

> The cpu_physical_memory_set_dirty_lebitmap() can quickly deal with
> the dirty pages of memory by bitmap-traveling, regardless of whether
> the bitmap is aligned correctly or not.
> 
> cpu_physical_memory_set_dirty_lebitmap() supports pages in bitmap of
> host page size. So it'd better to set bitmap_pgsize to host page size
> to support more translation granule sizes.
> 
> Fixes: 87ea529c502 (vfio: Get migration capability flags for container)
> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> ---
>  hw/vfio/common.c | 44 ++++++++++++++++++++++----------------------
>  1 file changed, 22 insertions(+), 22 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 6ff1daa763..69fb5083a4 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -378,7 +378,7 @@ static int vfio_dma_unmap_bitmap(VFIOContainer *container,
>  {
>      struct vfio_iommu_type1_dma_unmap *unmap;
>      struct vfio_bitmap *bitmap;
> -    uint64_t pages = TARGET_PAGE_ALIGN(size) >> TARGET_PAGE_BITS;
> +    uint64_t pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size;
>      int ret;
>  
>      unmap = g_malloc0(sizeof(*unmap) + sizeof(*bitmap));
> @@ -390,12 +390,12 @@ static int vfio_dma_unmap_bitmap(VFIOContainer *container,
>      bitmap = (struct vfio_bitmap *)&unmap->data;
>  
>      /*
> -     * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap of
> -     * TARGET_PAGE_SIZE to mark those dirty. Hence set bitmap_pgsize to
> -     * TARGET_PAGE_SIZE.
> +     * cpu_physical_memory_set_dirty_lebitmap() supports pages in bitmap of
> +     * qemu_real_host_page_size to mark those dirty. Hence set bitmap_pgsize
> +     * to qemu_real_host_page_size.


I don't see that this change is well supported by the code,
cpu_physical_memory_set_dirty_lebitmap() seems to operate on
TARGET_PAGE_SIZE, and the next three patch chunks take a detour through
memory listener code that seem unrelated to the change described in the
commit log.  This claims to fix something, what is actually broken?
Thanks,

Alex

>       */
>  
> -    bitmap->pgsize = TARGET_PAGE_SIZE;
> +    bitmap->pgsize = qemu_real_host_page_size;
>      bitmap->size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) /
>                     BITS_PER_BYTE;
>  
> @@ -674,16 +674,16 @@ static void vfio_listener_region_add(MemoryListener *listener,
>          return;
>      }
>  
> -    if (unlikely((section->offset_within_address_space & ~TARGET_PAGE_MASK) !=
> -                 (section->offset_within_region & ~TARGET_PAGE_MASK))) {
> +    if (unlikely((section->offset_within_address_space & ~qemu_real_host_page_mask) !=
> +                 (section->offset_within_region & ~qemu_real_host_page_mask))) {
>          error_report("%s received unaligned region", __func__);
>          return;
>      }
>  
> -    iova = TARGET_PAGE_ALIGN(section->offset_within_address_space);
> +    iova = REAL_HOST_PAGE_ALIGN(section->offset_within_address_space);
>      llend = int128_make64(section->offset_within_address_space);
>      llend = int128_add(llend, section->size);
> -    llend = int128_and(llend, int128_exts64(TARGET_PAGE_MASK));
> +    llend = int128_and(llend, int128_exts64(qemu_real_host_page_mask));
>  
>      if (int128_ge(int128_make64(iova), llend)) {
>          return;
> @@ -892,8 +892,8 @@ static void vfio_listener_region_del(MemoryListener *listener,
>          return;
>      }
>  
> -    if (unlikely((section->offset_within_address_space & ~TARGET_PAGE_MASK) !=
> -                 (section->offset_within_region & ~TARGET_PAGE_MASK))) {
> +    if (unlikely((section->offset_within_address_space & ~qemu_real_host_page_mask) !=
> +                 (section->offset_within_region & ~qemu_real_host_page_mask))) {
>          error_report("%s received unaligned region", __func__);
>          return;
>      }
> @@ -921,10 +921,10 @@ static void vfio_listener_region_del(MemoryListener *listener,
>           */
>      }
>  
> -    iova = TARGET_PAGE_ALIGN(section->offset_within_address_space);
> +    iova = REAL_HOST_PAGE_ALIGN(section->offset_within_address_space);
>      llend = int128_make64(section->offset_within_address_space);
>      llend = int128_add(llend, section->size);
> -    llend = int128_and(llend, int128_exts64(TARGET_PAGE_MASK));
> +    llend = int128_and(llend, int128_exts64(qemu_real_host_page_mask));
>  
>      if (int128_ge(int128_make64(iova), llend)) {
>          return;
> @@ -1004,13 +1004,13 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
>      range->size = size;
>  
>      /*
> -     * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap of
> -     * TARGET_PAGE_SIZE to mark those dirty. Hence set bitmap's pgsize to
> -     * TARGET_PAGE_SIZE.
> +     * cpu_physical_memory_set_dirty_lebitmap() supports pages in bitmap of
> +     * qemu_real_host_page_size to mark those dirty. Hence set bitmap's pgsize
> +     * to qemu_real_host_page_size.
>       */
> -    range->bitmap.pgsize = TARGET_PAGE_SIZE;
> +    range->bitmap.pgsize = qemu_real_host_page_size;
>  
> -    pages = TARGET_PAGE_ALIGN(range->size) >> TARGET_PAGE_BITS;
> +    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);
> @@ -1114,7 +1114,7 @@ static int vfio_sync_dirty_bitmap(VFIOContainer *container,
>                 section->offset_within_region;
>  
>      return vfio_get_dirty_bitmap(container,
> -                       TARGET_PAGE_ALIGN(section->offset_within_address_space),
> +                       REAL_HOST_PAGE_ALIGN(section->offset_within_address_space),
>                         int128_get64(section->size), ram_addr);
>  }
>  
> @@ -1655,10 +1655,10 @@ static void vfio_get_iommu_info_migration(VFIOContainer *container,
>                              header);
>  
>      /*
> -     * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap of
> -     * TARGET_PAGE_SIZE to mark those dirty.
> +     * cpu_physical_memory_set_dirty_lebitmap() supports pages in bitmap of
> +     * qemu_real_host_page_size to mark those dirty.
>       */
> -    if (cap_mig->pgsize_bitmap & TARGET_PAGE_SIZE) {
> +    if (cap_mig->pgsize_bitmap & qemu_real_host_page_size) {
>          container->dirty_pages_supported = true;
>          container->max_dirty_bitmap_size = cap_mig->max_dirty_bitmap_size;
>          container->dirty_pgsizes = cap_mig->pgsize_bitmap;