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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-06-07 14:10:24 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-06-13 13:03:41 +0200 |
| commit | 23fefe119ceb5fb0c7d3321010620010a4eddb18 (patch) | |
| tree | 28bb0f8eb256391130e3afc6527e9ef385c4b3ce /arch/s390/include/asm/ptrace.h | |
| parent | s390: rename struct psw_bits members (diff) | |
| download | linux-23fefe119ceb5fb0c7d3321010620010a4eddb18.tar.xz linux-23fefe119ceb5fb0c7d3321010620010a4eddb18.zip | |
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/ptrace.h')
| -rw-r--r-- | arch/s390/include/asm/ptrace.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h index 004f54909235..853b01245c20 100644 --- a/arch/s390/include/asm/ptrace.h +++ b/arch/s390/include/asm/ptrace.h @@ -11,9 +11,11 @@ #define PIF_SYSCALL 0 /* inside a system call */ #define PIF_PER_TRAP 1 /* deliver sigtrap on return to user */ +#define PIF_SYSCALL_RESTART 2 /* restart the current system call */ #define _PIF_SYSCALL _BITUL(PIF_SYSCALL) #define _PIF_PER_TRAP _BITUL(PIF_PER_TRAP) +#define _PIF_SYSCALL_RESTART _BITUL(PIF_SYSCALL_RESTART) #ifndef __ASSEMBLY__ |