Re: [Xen-devel] [PATCH RFC 2/8] public/io/netif: add directory for backend parameters

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Joao Martins [mailto:joao.m.martins@xxxxxxxxxx]
> Sent: 02 November 2017 18:06
> To: Xen Development List <xen-devel@xxxxxxxxxxxxx>
> Cc: Joao Martins <joao.m.martins@xxxxxxxxxx>; Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Wei Liu
> <wei.liu2@xxxxxxxxxx>
> Subject: [PATCH RFC 2/8] public/io/netif: add directory for backend
> parameters
> 
> The proposed directory provides a mechanism for tools to control the
> maximum feature set of the device being provisioned by backend.
> The parameters/features include offloading features, number of
> queues etc.
> 
> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> ---
>  xen/include/public/io/netif.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
> index 2454448baa..a412e4771d 100644
> --- a/xen/include/public/io/netif.h
> +++ b/xen/include/public/io/netif.h
> @@ -161,6 +161,22 @@
>   */
> 
>  /*
> + * The directory "require" maybe be created in backend path by tools
> + * domain to override the maximum feature set that backend provides to
> the
> + * frontend. The children entries within this directory are features names
> + * and the correspondent values that should be used backend as defaults
> e.g.:
> + *
> + * /local/domain/X/backend/<domid>/<handle>/require
> + * /local/domain/X/backend/<domid>/<handle>/require/multi-queue-
> max-queues = "2"
> + * /local/domain/X/backend/<domid>/<handle>/require/feature-no-csum-
> offload = "1"
> + *
> + * In the example above, network backend will negotiate up to a maximum
> of
> + * two queues with frontend plus disabling IPv4 checksum offloading.
> + *
> + * This directory and its children entries shall only be visible to the 
> backend.
> + */
> +

What should happen if the toolstack sets something in 'require' that the 
backend cannot provide? I don't see anything in your RFC patches to check that 
the backend has responded appropriately to the keys.

  Paul

> +/*
>   * Control ring
>   * ============
>   *
> --
> 2.11.0


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