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

[Christian Borntraeger]

On 08/23/2017 02:31 PM, Cornelia Huck wrote:
> On Wed, 23 Aug 2017 12:16:23 +0200
> Christian Borntraeger <address@hidden> 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 <address@hidden>
>> Cc: Alexander Graf <address@hidden>
>> Cc: Dan Horak <address@hidden>
>> Cc: David Hildenbrand <address@hidden>
>> Signed-off-by: Christian Borntraeger <address@hidden>
>> Acked-by: Janosch Frank <address@hidden>
>> ---
>> 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.

Sure. Looks like I forgot to add Thomas/Davids R-bs, so please add those.