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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2017-06-07 14:10:24 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-06-13 13:03:41 +0200
commit23fefe119ceb5fb0c7d3321010620010a4eddb18 (patch)
tree28bb0f8eb256391130e3afc6527e9ef385c4b3ce /arch/s390/Kconfig
parenta752598254016d2f9b4415d43a6402fe083f70b2 (diff)
downloadlinux-23fefe119ceb5fb0c7d3321010620010a4eddb18.tar.bz2
s390/kvm: avoid global config of vm.alloc_pgste=1
The system control vm.alloc_pgste is used to control the size of the page tables, either 2K or 4K. The idea is that a KVM host sets the vm.alloc_pgste control to 1 which causes *all* new processes to run with 4K page tables. For a non-kvm system the control should stay off to save on memory used for page tables. Trouble is that distributions choose to set the control globally to be able to run KVM guests. This wastes memory on non-KVM systems. Introduce the PT_S390_PGSTE ELF segment type to "mark" the qemu executable with it. All executables with this (empty) segment in its ELF phdr array will be started with 4K page tables. Any executable without PT_S390_PGSTE will run with the default 2K page tables. This removes the need to set vm.alloc_pgste=1 for a KVM host and minimizes the waste of memory for page tables. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/Kconfig')
-rw-r--r--arch/s390/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index e7ff58150e8f..bb11f9f30c8d 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -64,6 +64,7 @@ config ARCH_SUPPORTS_UPROBES
config S390
def_bool y
+ select ARCH_BINFMT_ELF_STATE
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_GCOV_PROFILE_ALL