On 18/06/2021 16:22, Andrew Cooper wrote:
> On 18/06/2021 16:06, Andrew Cooper wrote:
>> On 18/06/2021 11:25, Jan Beulich wrote:
>>> libxc generally uses uint32_t to represent domain IDs. This is fine as
>>> long as addresses of such variables aren't taken, to then pass into
>>> hypercalls: To the hypervisor, a domain ID is a 16-bit value. Use an
>>> intermediate variable to deal with the issue. (On architectures with
>>> arguments passed in registers, such an intermediate variable would have
>>> been created by the compiler already anyway, just one of the wrong
>>> type.)
>>>
>>> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>>>
>>> --- a/tools/libs/ctrl/xc_domain.c
>>> +++ b/tools/libs/ctrl/xc_domain.c
>>> @@ -856,7 +856,9 @@ int xc_domain_get_tsc_info(xc_interface
>>>
>>> int xc_domain_maximum_gpfn(xc_interface *xch, uint32_t domid, xen_pfn_t
>>> *gpfns)
>>> {
>>> - long rc = do_memory_op(xch, XENMEM_maximum_gpfn, &domid,
>>> sizeof(domid));
>>> + domid_t xen_domid = domid;
>>> + long rc = do_memory_op(xch, XENMEM_maximum_gpfn, &xen_domid,
>>> + sizeof(xen_domid));
>> Why on earth do we pass the domid in by pointer and not value?
> This is horrible.
>
> What we're logically doing is passing a pointer to struct
> xen_memory_$FOO { domid_t domid; }, except its all done by void
> pointers, and even the public header files don't provide a suitable
> structure.
>
> I think we really do want to retrofit a suitable structure in the public
> interface and use that, rather than to continue games like this.
Alternatively, declare this interface broken and reimplement it as a
domctl, which is where the functionality ought logically to live.
~Andrew
