From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38328) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dkQgt-0005dW-TI for qemu-devel@nongnu.org; Wed, 23 Aug 2017 04:07:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dkQgb-0005gA-S8 for qemu-devel@nongnu.org; Wed, 23 Aug 2017 04:07:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46756) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dkQgb-0005fD-Ge for qemu-devel@nongnu.org; Wed, 23 Aug 2017 04:06:49 -0400 References: <1503471212-109371-1-git-send-email-borntraeger@de.ibm.com> From: Thomas Huth Message-ID: Date: Wed, 23 Aug 2017 10:06:42 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] configure: enable --s390-pgste linker option List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Hildenbrand , Christian Borntraeger , Cornelia Huck Cc: qemu-devel , Alexander Graf , Janosch Frank , Christian Ehrhardt , Dan Horak On 23.08.2017 10:00, David Hildenbrand wrote: > On 23.08.2017 08:53, 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 >> Cc: Alexander Graf >> Cc: Dan Horak >> Cc: David Hildenbrand >> Signed-off-by: Christian Borntraeger >> Acked-by: Janosch Frank >> --- >> 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 >> } >> >> + > > I'd drop this new line > >> +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 $flag ; then >> LDFLAGS="-Wl,$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 "$kvm" = "yes"; then > > Wonder if the "$ARCH" check is really necessary: TARGET_ARCH=s390x with > kvm=yes should only build on s390x. Isn't kvm=yes and TARGET_ARCH=s390x also possible on a x86 host, where only the x86_64 target is built with CONFIG_KVM=y, but the s390x target with CONFIG_KVM=n ? Thomas