Re: [PATCH for-4.22] XSM: guard .sysctl() and .readconsole() hooks

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 18/06/2026 1:23 pm, Jan Beulich wrote:
> On 18.06.2026 14:13, Andrew Cooper wrote:
>> On 18/06/2026 12:32 pm, Jan Beulich wrote:
>>> Leaving the hook pointers in struct xsm_ops when !SYSCTL would lead to
>>> the BUG_ON() in xsm_fixup_ops() triggering for respectively configured
>>> hypervisors.
>>>
>>> While moving the #ifdef for the corresponding xsm_*() wrappers, also move
>>> those for xsm_page_offline() (where the hook pointer field already is
>>> suitably guarded).
>>>
>>> Fixes: c9eabaa03a68 ("xen/xsm: wrap around xsm_sysctl with CONFIG_SYSCTL")
>>> Fixes: bddd9af6049f ("xen/sysctl: wrap around XEN_SYSCTL_readconsole")
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Ugly.  We probably ought to see about booting the RANDCONFIG hypervisor
>> too, which should be able to spot things like this.
>>
>> This is a regression vs 4.21, so does need including.
> Aiui it's a regression vs 4.20, i.e. will want backporting to 4.21.
>
>> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although...
> Thanks.
>
>>> --- a/xen/include/xsm/xsm.h
>>> +++ b/xen/include/xsm/xsm.h
>>> @@ -61,8 +61,10 @@ struct xsm_ops {
>>>  #endif
>>>      int (*set_target)(struct domain *d, struct domain *e);
>>>      int (*domctl)(struct domain *d, struct xen_domctl *op);
>>> +#ifdef CONFIG_SYSCTL
>>>      int (*sysctl)(int cmd);
>>>      int (*readconsole)(uint32_t clear);
>>> +#endif
>> ... this is now the 3rd CONFIG_SYSCTL in xsm_ops.
>>
>> I know it will grow the diff, but can we see about collecting them into
>> a single region, and in dummy_ops too?  It will shrink the overall
>> result, and the order of pointers in this ops structure is uninteresting.
> I have a far more consolidating patch in the works, which is how I actually
> noticed the issue. I'd prefer to keep things as simple as possible here.

Ok.  Fine by me.

~Andrew