Re: [PATCH V2 1/2] vhost-vdpa: skip ram device from the IOTLB mapping

[Si-Wei Liu]

On 6/2/2021 1:41 AM, Jason Wang wrote:
> vDPA is not tie to any specific hardware, for safety and simplicity,
> vhost-vDPA doesn't allow MMIO area to be mapped via IOTLB. Only the
> doorbell could be mapped via mmap(). So this patch exclude skip the
> ram device from the IOTLB mapping.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
>   hw/virtio/vhost-vdpa.c | 12 ++----------
>   1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 01d2101d09..dd4321bac2 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -27,6 +27,8 @@ static bool 
> vhost_vdpa_listener_skipped_section(MemoryRegionSection *section)
>   {
>       return (!memory_region_is_ram(section->mr) &&
>               !memory_region_is_iommu(section->mr)) ||
> +           /* vhost-vDPA doesn't allow MMIO to be mapped  */
> +            memory_region_is_ram_device(section->mr) ||
>              /*
>               * Sizing an enabled 64-bit BAR can cause spurious mappings to
>               * addresses in the upper part of the 64-bit address space.  These
> @@ -171,22 +173,12 @@ static void vhost_vdpa_listener_region_add(MemoryListener 
> *listener,
>                                vaddr, section->readonly);
>       if (ret) {
>           error_report("vhost vdpa map fail!");
> -        if (memory_region_is_ram_device(section->mr)) {
> -            /* Allow unexpected mappings not to be fatal for RAM devices */
> -            error_report("map ram fail!");
> -          return ;
> -        }
>           goto fail;
>       }
>   
>       return;
>   
>   fail:
> -    if (memory_region_is_ram_device(section->mr)) {
> -        error_report("failed to vdpa_dma_map. pci p2p may not work");
> -        return;
> -
> -    }
>       /*
>        * On the initfn path, store the first error in the container so we
>        * can gracefully fail.  Runtime, there's not much we can do other