Re: [PATCH v2 18/26] xen/domctl: wrap xsm_getdomaininfo() with CONFIG_MGMT_HYPERCALLS

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.09.2025 11:41, Penny, Zheng wrote:
> [Public]
> 
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: Thursday, September 11, 2025 9:30 PM
>> To: Penny, Zheng <penny.zheng@xxxxxxx>
>> Cc: Huang, Ray <Ray.Huang@xxxxxxx>; Daniel P. Smith
>> <dpsmith@xxxxxxxxxxxxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
>> Subject: Re: [PATCH v2 18/26] xen/domctl: wrap xsm_getdomaininfo() with
>> CONFIG_MGMT_HYPERCALLS
>>
>> On 10.09.2025 09:38, Penny Zheng wrote:
>>> --- a/xen/include/xsm/xsm.h
>>> +++ b/xen/include/xsm/xsm.h
>>> @@ -55,8 +55,8 @@ struct xsm_ops {
>>>      void (*security_domaininfo)(struct domain *d,
>>>                                  struct xen_domctl_getdomaininfo *info);
>>>      int (*domain_create)(struct domain *d, uint32_t ssidref);
>>> -    int (*getdomaininfo)(struct domain *d);
>>>  #ifdef CONFIG_MGMT_HYPERCALLS
>>> +    int (*getdomaininfo)(struct domain *d);
>>>      int (*domctl_scheduler_op)(struct domain *d, int op);
>>>      int (*sysctl_scheduler_op)(int op);
>>>      int (*set_target)(struct domain *d, struct domain *e); @@ -234,7
>>> +234,11 @@ static inline int xsm_domain_create(
>>>
>>>  static inline int xsm_getdomaininfo(xsm_default_t def, struct domain
>>> *d)  {
>>> +#ifdef CONFIG_MGMT_HYPERCALLS
>>>      return alternative_call(xsm_ops.getdomaininfo, d);
>>> +#else
>>> +    return -EOPNOTSUPP;
>>> +#endif
>>>  }
>>
>> This is in use by a Xenstore sysctl and a Xenstore domctl. The sysctl is 
>> hence
>> already broken with the earlier series. Now the domctl is also being screwed 
>> up. I
>> don't think MGMT_HYPERCALLS really ought to extend to any operations 
>> available
>> to other than the core toolstack. That's the Xenstore ones here, but also 
>> the ones
>> used by qemu (whether run in Dom0 or a stubdom).
> 
> Maybe not only limited to the core toolstack. In dom0less/hyperlaunched 
> scenarios, hypercalls are strictly limited. QEMU is also limited to pvh 
> machine type and with very restricted functionality(, only acting as a few 
> virtio-pci devices backend). @Andryuk, Jason @Stabellini, Stefano Am I 
> understanding correctly and thoroughly about our scenario here for upstream?
> Tracking the codes, if Xenstore is created as a stub domain, it requires 
> getdomaininfo-domctl to acquire related info.  Sorry, I haven't found how it 
> was called in QEMU...

It's not "it"; it's different ones. First and foremost I was thinking of
 * XEN_DOMCTL_ioport_mapping
 * XEN_DOMCTL_memory_mapping
 * XEN_DOMCTL_bind_pt_irq
 * XEN_DOMCTL_unbind_pt_irq
but there may be others (albeit per the dummy xsm_domctl() this is the full
set). As a general criteria, anything using XSM_DM_PRIV checking can in
principle be called by qemu.

Jan