configure: enable --s390-pgste linker option
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> Reviewed-by: Thomas Huth <thuth@redhat.com> Message-Id: <1503483383-199649-1-git-send-email-borntraeger@de.ibm.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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@ -240,6 +240,11 @@ supported_target() {
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return 1
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}
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ld_has() {
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$ld --help 2>/dev/null | grep ".$1" >/dev/null 2>&1
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}
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# default parameters
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source_path=$(dirname "$0")
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cpu=""
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@ -5043,7 +5048,7 @@ fi
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# Use ASLR, no-SEH and DEP if available
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if test "$mingw32" = "yes" ; then
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for flag in --dynamicbase --no-seh --nxcompat; do
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if $ld --help 2>/dev/null | grep ".$flag" >/dev/null 2>/dev/null ; then
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if ld_has $flag ; then
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LDFLAGS="-Wl,$flag $LDFLAGS"
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fi
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done
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@ -6522,6 +6527,20 @@ if test "$target_linux_user" = "yes" -o "$target_bsd_user" = "yes" ; then
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ldflags="$ldflags $textseg_ldflags"
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fi
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# Newer kernels on s390 check for an S390_PGSTE program header and
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# enable the pgste page table extensions in that case. This makes
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# the vm.allocate_pgste sysctl unnecessary. We enable this program
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# header if
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# - we build on s390x
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# - we build the system emulation for s390x (qemu-system-s390x)
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# - KVM is enabled
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# - the linker supports --s390-pgste
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if test "$TARGET_ARCH" = "s390x" -a "$target_softmmu" = "yes" -a "$ARCH" = "s390x" -a "$kvm" = "yes"; then
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if ld_has --s390-pgste ; then
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ldflags="-Wl,--s390-pgste $ldflags"
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fi
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fi
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echo "LDFLAGS+=$ldflags" >> $config_target_mak
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echo "QEMU_CFLAGS+=$cflags" >> $config_target_mak
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