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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/kernel | |
| parent | a752598254016d2f9b4415d43a6402fe083f70b2 (diff) | |
| download | linux-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/kernel')
| -rw-r--r-- | arch/s390/kernel/entry.S | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 6315037335ba..0c0138c7dfc7 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -52,7 +52,7 @@ _TIF_TRACE = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \ _TIF_SYSCALL_TRACEPOINT) _CIF_WORK = (_CIF_MCCK_PENDING | _CIF_ASCE_PRIMARY | \ _CIF_ASCE_SECONDARY | _CIF_FPU) -_PIF_WORK = (_PIF_PER_TRAP) +_PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART) #define BASED(name) name-cleanup_critical(%r13) @@ -334,6 +334,8 @@ ENTRY(system_call) jo .Lsysc_mcck_pending TSTMSK __TI_flags(%r12),_TIF_NEED_RESCHED jo .Lsysc_reschedule + TSTMSK __PT_FLAGS(%r11),_PIF_SYSCALL_RESTART + jo .Lsysc_syscall_restart #ifdef CONFIG_UPROBES TSTMSK __TI_flags(%r12),_TIF_UPROBE jo .Lsysc_uprobe_notify @@ -347,6 +349,8 @@ ENTRY(system_call) jo .Lsysc_patch_pending # handle live patching just before # signals and possible syscall restart #endif + TSTMSK __PT_FLAGS(%r11),_PIF_SYSCALL_RESTART + jo .Lsysc_syscall_restart TSTMSK __TI_flags(%r12),_TIF_SIGPENDING jo .Lsysc_sigpending TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME @@ -448,6 +452,15 @@ ENTRY(system_call) jg do_per_trap # +# _PIF_SYSCALL_RESTART is set, repeat the current system call +# +.Lsysc_syscall_restart: + ni __PT_FLAGS+7(%r11),255-_PIF_SYSCALL_RESTART + lmg %r1,%r7,__PT_R1(%r11) # load svc arguments + lg %r2,__PT_ORIG_GPR2(%r11) + j .Lsysc_do_svc + +# # call tracehook_report_syscall_entry/tracehook_report_syscall_exit before # and after the system call # |