Re: [PATCH v2 for-4.14] x86/livepatch: Make livepatching compatible with CET Shadow Stacks

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.06.2020 15:59, Ross Lagerwall wrote:
> On 2020-06-26 13:24, Andrew Cooper wrote:
>> @@ -56,18 +57,48 @@ int arch_livepatch_safety_check(void)
>>      return -EBUSY;
>>  }
>>  
>> -int arch_livepatch_quiesce(void)
>> +int noinline arch_livepatch_quiesce(void)
>>  {
>> +    /* If Shadow Stacks are in use, disable CR4.CET so we can modify 
>> CR0.WP. */
>> +    if ( cpu_has_xen_shstk )
> 
> Should this be:
>     if ( IS_ENABLED(CONFIG_XEN_SHSTK) && cpu_has_xen_shstk )
> 
> to match arch_livepatch_revive?

While it may look a little asymmetric, I think it's preferable
to is IS_ENABLED() only where really needed, i.e. here it
guarding code that otherwise may not build.

Jan