Re: [RFC/PATCH 20/22] s390/mm: Enable gmap huge pmd support

Janosch Frank
2017-11-15T12:24:18Z

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On 15.11.2017 11:08, David Hildenbrand wrote:
> On 06.11.2017 23:29, Janosch Frank wrote:
>> Now that we have everything in place, let's allow huge pmds for gmap
>> linking, effectively allowing huge pages guests.
>
> Can you add a comment about transparent huge pages?

Now that we have everything in place, let's allow huge (1m) pmds for
gmap linking, effectively allowing hugetlbfs backed guests. Transparent
huge pages and 2g huge pages are *not* supported through this change.

>
> Reviewed-by: David Hildenbrand <david@redhat.com>

Thanks!

>
>>
>> Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
>> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
>> ---
>> arch/s390/mm/gmap.c | 7 +++----
>> 1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
>> index 430dcd9..3cc2765 100644
>> --- a/arch/s390/mm/gmap.c
>> +++ b/arch/s390/mm/gmap.c
>> @@ -1,8 +1,10 @@
>> /*
>> * KVM guest address space mapping code
>> *
>> - * Copyright IBM Corp. 2007, 2016
>> + * Copyright IBM Corp. 2007, 2016, 2017
>> * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
>> + * David Hildenbrand <david@redhat.com>
>> + * Janosch Frank <frankja@linux.vnet.ibm.com>
>> */
>>
>> #include <linux/kernel.h>
>> @@ -596,9 +598,6 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
>> return -EFAULT;
>> pmd = pmd_offset(pud, vmaddr);
>> VM_BUG_ON(pmd_none(*pmd));
>> - /* large pmds cannot yet be handled */
>> - if (pmd_large(*pmd))
>> - return -EFAULT;
>> /* Link gmap segment table entry location to page table. */
>> rc = radix_tree_preload(GFP_KERNEL);
>> if (rc)
>>
>
>

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