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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.08.17 at 17:57, <jgross@xxxxxxxx> wrote:
> On 15/08/17 17:39, Jan Beulich wrote:
>>>>> On 14.08.17 at 09:08, <jgross@xxxxxxxx> wrote:
>>> +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.
> 
> Would this help in any way?

Since the caller won't want to dimension the buffer dynamically,
perhaps not much. The only use I could see would be to give a
better error message for too long strings than the one resulting
from strerror(). I.e. ...

> Maybe just returning E2BIG would be enough?

... maybe yes.

Jan


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