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Diffstat (limited to 'arch/powerpc/kernel/time.c')
| -rw-r--r-- | arch/powerpc/kernel/time.c | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index fa7c4f12104f..7316dd15278a 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -621,6 +621,38 @@ unsigned long long sched_clock(void) return mulhdu(get_tb() - boot_tb, tb_to_ns_scale) << tb_to_ns_shift; } + +#ifdef CONFIG_PPC_PSERIES + +/* + * Running clock - attempts to give a view of time passing for a virtualised + * kernels. + * Uses the VTB register if available otherwise a next best guess. + */ +unsigned long long running_clock(void) +{ + /* + * Don't read the VTB as a host since KVM does not switch in host + * timebase into the VTB when it takes a guest off the CPU, reading the + * VTB would result in reading 'last switched out' guest VTB. + * + * Host kernels are often compiled with CONFIG_PPC_PSERIES checked, it + * would be unsafe to rely only on the #ifdef above. + */ + if (firmware_has_feature(FW_FEATURE_LPAR) && + cpu_has_feature(CPU_FTR_ARCH_207S)) + return mulhdu(get_vtb() - boot_tb, tb_to_ns_scale) << tb_to_ns_shift; + + /* + * This is a next best approximation without a VTB. + * On a host which is running bare metal there should never be any stolen + * time and on a host which doesn't do any virtualisation TB *should* equal + * VTB so it makes no difference anyway. + */ + return local_clock() - cputime_to_nsecs(kcpustat_this_cpu->cpustat[CPUTIME_STEAL]); +} +#endif + static int __init get_freq(char *name, int cells, unsigned long *val) { struct device_node *cpu; |