Re: [PATCH v2 2/3] memory: Allow a MemoryRegion to be marked no_vhost

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jan 13, 2020 at 05:36:46PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Allow a memory region to be marked as 'no_vhost' and
> exclude that region from vhost's list build.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

I thought we agreed vfio needs this as well?
I'd rather this had some meaning not just "no vhost" ...
no_dma?

> ---
>  hw/virtio/vhost.c     |  3 ++-
>  include/exec/memory.h | 21 +++++++++++++++++++++
>  memory.c              | 15 +++++++++++++++
>  3 files changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 774d87d98e..462498bfe6 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -402,7 +402,8 @@ static bool vhost_section(struct vhost_dev *dev, MemoryRegionSection *section)
>      bool log_dirty = memory_region_get_dirty_log_mask(section->mr) &
>                       ~(1 << DIRTY_MEMORY_MIGRATION);
>      result = memory_region_is_ram(section->mr) &&
> -        !memory_region_is_rom(section->mr);
> +             !memory_region_is_rom(section->mr) &&
> +             !memory_region_get_no_vhost(section->mr);
>  
>      /* Vhost doesn't handle any block which is doing dirty-tracking other
>       * than migration; this typically fires on VGA areas.
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index aef8123d48..f475c06d63 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -394,6 +394,7 @@ struct MemoryRegion {
>      bool ram_device;
>      bool enabled;
>      bool warning_printed; /* For reservations */
> +    bool no_vhost;
>      uint8_t vga_logging_count;
>      MemoryRegion *alias;
>      hwaddr alias_offset;
> @@ -1625,6 +1626,26 @@ void memory_region_set_readonly(MemoryRegion *mr, bool readonly);
>   */
>  void memory_region_set_nonvolatile(MemoryRegion *mr, bool nonvolatile);
>  
> +/**
> + * memory_region_set_no_vhost: Make vhost ignore a memory region
> + *
> + * Makes vhost ignore a memory region, useful if it isn't real
> + * DMAble memory and is at inconvenient addresses
> + *
> + * @mr: the region being updated.
> + * @no_vhost: true to ignore
> + */
> +void memory_region_set_no_vhost(MemoryRegion *mr, bool no_vhost);
> +
> +/**
> + * memory_region_set_no_vhost: Test if memory region is marked no vhost
> + *
> + * Test if the no_vhost flag is set on the memory region
> + *
> + * @mr: the region being tested.
> + */
> +bool memory_region_get_no_vhost(const MemoryRegion *mr);
> +
>  /**
>   * memory_region_rom_device_set_romd: enable/disable ROMD mode
>   *
> diff --git a/memory.c b/memory.c
> index d7b9bb6951..9371998e30 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -2136,6 +2136,21 @@ void memory_region_set_nonvolatile(MemoryRegion *mr, bool nonvolatile)
>      }
>  }
>  
> +void memory_region_set_no_vhost(MemoryRegion *mr, bool no_vhost)
> +{
> +    if (mr->no_vhost != no_vhost) {
> +        memory_region_transaction_begin();
> +        mr->no_vhost = no_vhost;
> +        memory_region_update_pending |= mr->enabled;
> +        memory_region_transaction_commit();
> +    }
> +}
> +
> +bool memory_region_get_no_vhost(const MemoryRegion *mr)
> +{
> +    return mr->no_vhost;
> +}
> +
>  void memory_region_rom_device_set_romd(MemoryRegion *mr, bool romd_mode)
>  {
>      if (mr->romd_mode != romd_mode) {
> -- 
> 2.24.1