On 23.08.2017 08:55, Christian Borntraeger wrote:
>
>
> On 08/23/2017 08:53 AM, Christian Borntraeger 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.ehrha...@canonical.com>
>> Cc: Alexander Graf <ag...@suse.de>
>> Cc: Dan Horak <dho...@redhat.com>
>> Cc: David Hildenbrand <da...@redhat.com>
>> Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>
>> Acked-by: Janosch Frank <fran...@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
>>
>> configure | 21 ++++++++++++++++++++-
>> 1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure b/configure
>> index dd73cce..0b68b37 100755
>> --- a/configure
>> +++ b/configure
>> @@ -240,6 +240,11 @@ supported_target() {
>> return 1
>> }
>>
>> +
>> +ld_has() {
>> + $ld --help 2>/dev/null | grep ".$1" >/dev/null 2>&1
>> +}
>> +
>> # default parameters
>> source_path=$(dirname "$0")
>> cpu=""
>> @@ -5043,7 +5048,7 @@ fi
>> # Use ASLR, no-SEH and DEP if available
>> if test "$mingw32" = "yes" ; then
>> for flag in --dynamicbase --no-seh --nxcompat; do
>> - if $ld --help 2>/dev/null | grep ".$flag" >/dev/null 2>/dev/null ;
>> then
>> + if ld_had $flag ; then
>
> typo, will fix with v3 :-/
>
>
>> LDFLAGS="-Wl,$flag $LDFLAGS"
>> fi
>> done
>> @@ -6522,6 +6527,20 @@ if test "$target_linux_user" = "yes" -o
>> "$target_bsd_user" = "yes" ; then
>> ldflags="$ldflags $textseg_ldflags"
>> fi
>>
>> +# Newer kernels on s390 check for an S390_PGSTE program header and
>> +# enable the pgste page table extensions in that case. This makes
>> +# the vm.allocate_pgste sysctl unnecessary. We enable this program
>> +# header if
>> +# - we build on s390x
>> +# - we build the system emulation for s390x (qemu-system-s390x)
>> +# - KVM is enabled
>> +# - the linker support --s390-pgste
>> +if test "$TARGET_ARCH" = "s390x" -a "$target_softmmu" = "yes" -a "$ARCH" =
>> "s390x" -a "$kvm" = "yes"; then
>> + if ld_has --s390-pgste ; then
>> + ldflags="-Wl,--s390-pgste $ldflags"
>> + fi
>> +fi
>> +
>> echo "LDFLAGS+=$ldflags" >> $config_target_mak
>> echo "QEMU_CFLAGS+=$cflags" >> $config_target_mak
Apart from the typo, this looks good to me. Feel free to add my
Reviewed-by: Thomas Huth <th...@redhat.com>
once you've fixed the typo.
Thomas
