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.
~Andrew
