Re: [RFC/PATCH 02/22] s390/mm: Abstract gmap notify bit setting

David Hildenbrand
2017-11-15T09:30:30Z

On 13.11.2017 16:57, Janosch Frank wrote:
> On 10.11.2017 13:57, David Hildenbrand wrote:
>> On 06.11.2017 23:29, Janosch Frank wrote:
>>> Currently we use the software PGSTE bits PGSTE_IN_BIT and PGSTE_VSIE_BIT
>>> to notify before an invalidation occurs on a prefix page or a VSIE page
>>> respectively. Both bits only work for a PGSTE, which only exists for
>>> page tables.
>>>
>>> For huge page support we also need such bits for segments (pmds) so
>>> let's introduce abstract GMAP_ENTRY_* bits that will be realized into
>>> the respective bits when gmap DAT table entries are protected.
>>>
>>> Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
>>> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> [...]
>>> @@ -8,6 +8,10 @@
>>> #ifndef _ASM_S390_GMAP_H
>>> #define _ASM_S390_GMAP_H
>>>
>>> +/* Generic bits for GMAP notification on DAT table entry changes. */
>>> +#define GMAP_ENTRY_VSIE 0x2
>>> +#define GMAP_ENTRY_IN 0x1
>>
>> Can we rename
>> GMAP_ENTRY_VSIE -> GMAP_ENTRY_SHADOW_IN
>>
>> and also
>>
>> PGSTE_VSIE_BIT -> PGSTE_SHADOW_IN_BIT
>
> I'd like to keep the PGSTE bit names, the PGSTE bits are nicely
> formatted and consistent in pgtable.h. The segment bit names are even
> worse because of their length:
>
> _SEGMENT_ENTRY_GMAP_VSIE
>
> and if we'd use your naming it gets even longer:
>
> _SEGMENT_ENTRY_GMAP_SHADOW_IN_BIT
>
>
> I'll try to come up with something consistent and good sounding, but it
> certainly isn't a #1 priority and I might fail to do so :)
>
>>
>> as they are used for managing shadow page table invalidation.
>>
>> Also, a better fitting name for ENTRY would be nice :)
>> (GMAP_NOTIFY_...)
>
> Yes, the ENTRY part came from the _SEGMENT_ENTRY_* constants, whose
> names you might also dislike.
>
> So I think I'll use:
> GMAP_NOTIFY_PREFIX(_BIT)

s/PREFIX/MPROTECT/ ?

Because that's the GMAP interface being used.

> GMAP_NOTIFY_SHADOW(_BIT)
>
>

--

Thanks,

David / dhildenb