Re: [PATCH v4 05/11] vfio: Query and store the maximum number of possible DMA mappings

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

On Thu,  7 Jan 2021 14:34:17 +0100
David Hildenbrand <david@redhat.com> wrote:

> Let's query the maximum number of possible DMA mappings by querying the
> available mappings when creating the container (before any mappings are
> created). We'll use this informaton soon to perform some sanity checks
> and warn the user.
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Auger Eric <eric.auger@redhat.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: teawater <teawaterz@linux.alibaba.com>
> Cc: Marek Kedzierski <mkedzier@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/vfio/common.c              | 4 ++++
>  include/hw/vfio/vfio-common.h | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 2bd219cf1d..1babb6bb99 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1934,6 +1934,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>      container->fd = fd;
>      container->error = NULL;
>      container->dirty_pages_supported = false;
> +    container->dma_max_mappings = 0;
>      QLIST_INIT(&container->giommu_list);
>      QLIST_INIT(&container->hostwin_list);
>      QLIST_INIT(&container->vrdl_list);
> @@ -1965,7 +1966,10 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>          vfio_host_win_add(container, 0, (hwaddr)-1, info->iova_pgsizes);
>          container->pgsizes = info->iova_pgsizes;
>  
> +        /* The default in the kernel ("dma_entry_limit") is 65535. */
> +        container->dma_max_mappings = 65535;
>          if (!ret) {
> +            vfio_get_info_dma_avail(info, &container->dma_max_mappings);
>              vfio_get_iommu_info_migration(container, info);
>          }
>          g_free(info);
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index af6f8d1b22..4b28c6e8ac 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -88,6 +88,7 @@ typedef struct VFIOContainer {
>      uint64_t dirty_pgsizes;
>      uint64_t max_dirty_bitmap_size;
>      unsigned long pgsizes;
> +    unsigned int dma_max_mappings;
>      QLIST_HEAD(, VFIOGuestIOMMU) giommu_list;
>      QLIST_HEAD(, VFIOHostDMAWindow) hostwin_list;
>      QLIST_HEAD(, VFIOGroup) group_list;

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>