Re: [Qemu-devel] [RFC 3/7] vhost: New memory update functions

[Igor Mammedov]

On Wed, 29 Nov 2017 18:50:22 +0000
"Dr. David Alan Gilbert (git)" <address@hidden> wrote:

> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> vhost_update_mem will replace the existing update mechanism.
> They make use of the Flatview we have now to make the update simpler.
> This commit just adds the basic structure.
see below suggestion on dropping vhost_region_add/vhost_region_del

> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  hw/virtio/vhost.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 938253d1e8..c959a59fb3 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -629,6 +629,43 @@ static void vhost_begin(MemoryListener *listener)
>      dev->mem_changed_start_addr = -1;
>  }
>  
> +struct vhost_update_mem_tmp {
> +    struct vhost_dev   *dev;
> +    uint32_t nregions;
> +    struct vhost_memory_region *regions;
> +};
> +
> +/* Called for each MRS from vhost_update_mem */
> +static int vhost_update_mem_cb(MemoryRegionSection *mrs, void *opaque)
> +{
> +    if (!vhost_section(mrs)) {
> +        return 0;
> +    }
> +
it's possible to move section tracking from vhost_region_add() to here

    ++dev->n_mem_sections;                                                      
 
    dev->mem_sections = g_renew(MemoryRegionSection, dev->mem_sections,         
 
                                dev->n_mem_sections);                           
 
    ;[dev->n_mem_sections - 1] = *section;                       
    memory_region_ref(section->mr);  
...

> +static int vhost_update_mem(struct vhost_dev *dev)
> +{
> +    int res;
> +    struct vhost_update_mem_tmp vtmp;
> +    vtmp.regions = 0;
> +    vtmp.nregions = 0;
> +    vtmp.dev = dev;
       
 iterate over dev->mem_sections
    memory_region_unref(section->mr);
 g_free(dev->mem_sections)
 dev->mem_sections = NULL;

with this you won't need vhost_region_add/del callbacks anymore


> +
> +    res = address_space_iterate(&address_space_memory,
> +                                vhost_update_mem_cb, &vtmp);
> +    if (res) {
> +        goto out;
> +    }
> +
> +    /* TODO */
> +out:
> +    g_free(vtmp.regions);
> +    return res;
> +}
> +
>  static void vhost_commit(MemoryListener *listener)
>  {
>      struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> @@ -648,6 +685,10 @@ static void vhost_commit(MemoryListener *listener)
>          return;
>      }
>  
> +    if (vhost_update_mem(dev)) {
> +        return;
> +    }
> +
>      if (dev->started) {
>          start_addr = dev->mem_changed_start_addr;
>          size = dev->mem_changed_end_addr - dev->mem_changed_start_addr + 1;
> @@ -1523,6 +1564,9 @@ int vhost_dev_start(struct vhost_dev *hdev, 
> VirtIODevice *vdev)
>          goto fail_features;
>      }
>  
> +    if (vhost_update_mem(hdev)) {
> +        goto fail_mem;
> +    }
>      if (vhost_dev_has_iommu(hdev)) {
>          memory_listener_register(&hdev->iommu_listener, vdev->dma_as);
>      }