Re: [Qemu-devel] [PATCH v3] configure: enable --s390-pgste linker option

[David Hildenbrand <david@redhat.com>]

On 23.08.2017 14:31, Cornelia Huck wrote:
> On Wed, 23 Aug 2017 12:16:23 +0200
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> 
>> KVM guests on s390 need a different page table layout than normal
>> processes (2kb page table + 2kb page status extensions vs 2kb page table
>> only). As of today this has to be enabled via the vm.allocate_pgste
>> sysctl.
>>
>> Newer kernels (>= 4.12) on s390 check for an S390_PGSTE program header
>> and enable the pgste page table extensions in that case. This makes the
>> vm.allocate_pgste sysctl unnecessary. We enable this program header for
>> the s390 system emulation (qemu-system-s390x) if we build on s390
>> - for s390 system emulation
>> - the linker supports --s390-pgste (binutils >= 2.29)
>> - KVM is enabled
>>
>> This will allow distributions to disable the global vm.allocate_pgste
>> sysctl, which will improve the page table allocation for non KVM
>> processes as only 2kb chunks are necessary.
>>
>> Cc: Christian Ehrhardt <christian.ehrhardt@canonical.com>
>> Cc: Alexander Graf <agraf@suse.de>
>> Cc: Dan Horak <dhorak@redhat.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> Acked-by: Janosch Frank <frankja@linux.vnet.ibm.com>
>> ---
>> V1->V2:
>> 	- provide ld_has function
>> 	- use ld_has to replace some open coded variants
>> 	- check target arch and arch for s390
>> 	- check for s390x before calling the linker
>> V2->V3: 
>> 	- fix typos
>>  configure | 21 ++++++++++++++++++++-
>>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> Looks sane.
> 
> I guess I'll wait for some more Acks or R-bs and then queue it to
> s390-next.
> 

My r-b still holds

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

-- 

Thanks,

David