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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.06.2026 14:51, Jan Beulich wrote:
> On 18.06.2026 14:48, Daniel P. Smith wrote:
>> On 6/18/26 8:42 AM, Jan Beulich wrote:
>>> On 18.06.2026 14:34, Daniel P. Smith wrote:
>>>> On 6/18/26 8:23 AM, 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.
>>>>
>>>> By the way, I was going back through this and notices that they are not
>>>> ifdef out in xsm/dummy.h. Are we relying on them being inlines to ensure
>>>> that they do not result in dead code?
>>>
>>> I think so. Maybe it's unhelpful that we have
>>
>> To be clear, you want to leave as is for now (or at least pick up in 
>> another patch)?
> 
> It's up to you - I can add the #ifdef there, but it doesn't look to strictly
> be needed.

Can you please make explicit which way you'd like it in order to provide an
ack, so this bug fix can go in?

Jan