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Re: [Qemu-devel] [PATCH v3] configure: enable --s390-pgste linker option
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH v3] configure: enable --s390-pgste linker option |
Date: |
Wed, 23 Aug 2017 17:09:17 +0200 |
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(-)
Thanks, applied.