Re: [PATCH 1/1] virtio-pci: return RAM device MR when set host notifier success

[Michael S. Tsirkin]

On Mon, Aug 12, 2024 at 08:20:27PM +0800, Gao Shiyuan wrote:
> When vhost-user backend register memory region based host notifiers,
> we should return RAM device MR of notify region MR's subregion in
> virtio_address_space_lookup.
> 
> In seabios, it will use virtio PCI Configration Access Capability
> access notify region when assign notify region above 4GB. This will
> exit to QEMU and invoke virtio_address_space_write. When vhost-user
> backend register memory region based host notifiers, return RAM device
> MR instead of notify region MR is suitable.


I can't really parse this.

> Co-developed-by: Zuo Boqun <zuoboqun@baidu.com>
> Signed-off-by: Gao Shiyuan <gaoshiyuan@baidu.com>
> Signed-off-by: Zuo Boqun <zuoboqun@baidu.com>

CC Jason

> ---
>  hw/virtio/virtio-pci.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 9534730bba..167ac9718a 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -610,13 +610,22 @@ static MemoryRegion 
> *virtio_address_space_lookup(VirtIOPCIProxy *proxy,
>  {
>      int i;
>      VirtIOPCIRegion *reg;
> +    MemoryRegion *mr, *submr;
>  
>      for (i = 0; i < ARRAY_SIZE(proxy->regs); ++i) {
>          reg = &proxy->regs[i];
>          if (*off >= reg->offset &&
>              *off + len <= reg->offset + reg->size) {
>              *off -= reg->offset;
> -            return &reg->mr;
> +            mr = &reg->mr;
> +            QTAILQ_FOREACH(submr, &mr->subregions, subregions_link) {
> +                if (*off >= submr->addr &&
> +                    *off + len < submr->addr + submr->size) {
> +                    *off -= submr->addr;
> +                    return submr;
> +                }
> +            }
> +            return mr;
>          }
>      }

Poking at internals of MR like this is not nice.
Doesn't memory_region_find work for this?



>  
> -- 
> 2.39.3 (Apple Git-146)