Re: [PATCH v4 2/5] softmmu: Support concurrent bounce buffers

[Peter Xu <peterx@redhat.com>]

On Tue, Sep 19, 2023 at 09:08:10AM -0700, Mattias Nissler wrote:
> @@ -3119,31 +3143,35 @@ void *address_space_map(AddressSpace *as,
>  void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
>                           bool is_write, hwaddr access_len)
>  {
> -    if (buffer != as->bounce.buffer) {
> -        MemoryRegion *mr;
> -        ram_addr_t addr1;
> +    MemoryRegion *mr;
> +    ram_addr_t addr1;
> +
> +    mr = memory_region_from_host(buffer, &addr1);
> +    if (mr == NULL) {
> +        BounceBuffer *bounce = container_of(buffer, BounceBuffer, buffer);
> +        assert(bounce->magic == BOUNCE_BUFFER_MAGIC);
>  
> -        mr = memory_region_from_host(buffer, &addr1);
> -        assert(mr != NULL);
>          if (is_write) {
> -            invalidate_and_set_dirty(mr, addr1, access_len);
> -        }
> -        if (xen_enabled()) {
> -            xen_invalidate_map_cache_entry(buffer);
> +            address_space_write(as, bounce->addr, MEMTXATTRS_UNSPECIFIED,
> +                                bounce->buffer, access_len);
>          }
> -        memory_region_unref(mr);
> +
> +        memory_region_unref(bounce->mr);
> +        qatomic_sub(&as->bounce_buffer_size, bounce->len);
> +        /* Write bounce_buffer_size before reading map_client_list. */
> +        smp_mb();
> +        address_space_notify_map_clients(as);
> +        bounce->magic = ~BOUNCE_BUFFER_MAGIC;
> +        g_free(bounce);
>          return;
>      }
> +
> +    if (xen_enabled()) {
> +        xen_invalidate_map_cache_entry(buffer);
> +    }
>      if (is_write) {
> -        address_space_write(as, as->bounce.addr, MEMTXATTRS_UNSPECIFIED,
> -                            as->bounce.buffer, access_len);
> -    }
> -    qemu_vfree(as->bounce.buffer);
> -    as->bounce.buffer = NULL;
> -    memory_region_unref(as->bounce.mr);

This line needs to be kept?

> -    /* Clear in_use before reading map_client_list.  */
> -    qatomic_set_mb(&as->bounce.in_use, false);
> -    address_space_notify_map_clients(as);
> +        invalidate_and_set_dirty(mr, addr1, access_len);
> +    }
>  }

-- 
Peter Xu