Re: [Xen-devel] [PATCH v2 48/52] xen: add hypercall for setting parameters at runtime

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.08.17 at 09:08, <jgross@xxxxxxxx> wrote:
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -1096,6 +1096,23 @@ struct xen_sysctl_livepatch_op {
>  typedef struct xen_sysctl_livepatch_op xen_sysctl_livepatch_op_t;
>  DEFINE_XEN_GUEST_HANDLE(xen_sysctl_livepatch_op_t);
>  
> +/*
> + * XEN_SYSCTL_set_parameter
> + *
> + * Change hypervisor parameters at runtime.
> + * The input string is parsed similar to the boot parameters.
> + */
> +
> +#define XEN_SET_PARAMETER_MAX_SIZE 1023

Does this really need to be in the public interface, i.e. isn't this limit
an implementation detail?

> +struct xen_sysctl_set_parameter {
> +    XEN_GUEST_HANDLE_64(char) params;       /* IN: pointer to parameters. */
> +    uint16_t size;                          /* IN: size of parameters. Max.
> +                                               XEN_SET_PARAMETER_MAX_SIZE. */

You could even allow querying the size by passing in a null handle
and returning the value in the size field.

> +    uint16_t pad[3];                        /* IN: MUST be zero. */

But you don't check the field is zero afaics.

Jan


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