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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-06-07 15:10:24 +0300 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-06-13 14:03:41 +0300 |
| commit | 23fefe119ceb5fb0c7d3321010620010a4eddb18 (patch) | |
| tree | 28bb0f8eb256391130e3afc6527e9ef385c4b3ce /arch/s390/include/asm/thread_info.h | |
| parent | a752598254016d2f9b4415d43a6402fe083f70b2 (diff) | |
| download | linux-23fefe119ceb5fb0c7d3321010620010a4eddb18.tar.xz | |
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/include/asm/thread_info.h')
| -rw-r--r-- | arch/s390/include/asm/thread_info.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h index 0b3ee083a665..1aecf432c48d 100644 --- a/arch/s390/include/asm/thread_info.h +++ b/arch/s390/include/asm/thread_info.h @@ -58,6 +58,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); #define TIF_UPROBE 3 /* breakpointed or single-stepping */ #define TIF_GUARDED_STORAGE 4 /* load guarded storage control block */ #define TIF_PATCH_PENDING 5 /* pending live patching update */ +#define TIF_PGSTE 6 /* New mm's will use 4K page tables */ #define TIF_31BIT 16 /* 32bit process */ #define TIF_MEMDIE 17 /* is terminating due to OOM killer */ |