The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=26d105199ec89d6eaec8a9ca70e3b05ca65e3aac
commit 26d105199ec89d6eaec8a9ca70e3b05ca65e3aac Author: Mark Johnston <[email protected]> AuthorDate: 2023-02-03 15:53:20 +0000 Commit: Mark Johnston <[email protected]> CommitDate: 2023-02-03 16:47:11 +0000 libc: Fall back to rdtsc when using pvclock and rdtscp is not available In preparation for a follow-up revision wherein kvmclock may export timekeeping info to userspace even in the absence of AMDID_RDTSCP, fall back to using rdtsc when rdtscp isn't available. This mimics pvclock_read_time_info() in the kernel. Reviewed by: kib Tested by: Shrikanth R Kamath <[email protected]> MFC after: 2 weeks Sponsored by: Klara, Inc. Sponsored by: Juniper Networks, Inc. Differential Revision: https://reviews.freebsd.org/D38341 --- lib/libc/x86/sys/__vdso_gettc.c | 42 ++++++++++++++++++++++++++++++++++++++--- 1 file changed, 39 insertions(+), 3 deletions(-) diff --git a/lib/libc/x86/sys/__vdso_gettc.c b/lib/libc/x86/sys/__vdso_gettc.c index b3f3de9f4203..7159d46c0113 100644 --- a/lib/libc/x86/sys/__vdso_gettc.c +++ b/lib/libc/x86/sys/__vdso_gettc.c @@ -101,6 +101,13 @@ rdtsc32_mb_lfence(void) return (rdtsc32()); } +static uint64_t +rdtsc_mb_lfence(void) +{ + lfence(); + return (rdtsc()); +} + static u_int rdtsc32_mb_mfence(void) { @@ -108,38 +115,62 @@ rdtsc32_mb_mfence(void) return (rdtsc32()); } +static uint64_t +rdtsc_mb_mfence(void) +{ + mfence(); + return (rdtsc()); +} + static u_int rdtsc32_mb_none(void) { return (rdtsc32()); } +static uint64_t +rdtsc_mb_none(void) +{ + return (rdtsc()); +} + static u_int rdtscp32_(void) { return (rdtscp32()); } +static uint64_t +rdtscp_(void) +{ + return (rdtscp()); +} + struct tsc_selector_tag { u_int (*ts_rdtsc32)(void); + uint64_t (*ts_rdtsc)(void); u_int (*ts_rdtsc_low)(const struct vdso_timehands *); }; static const struct tsc_selector_tag tsc_selector[] = { [0] = { /* Intel, LFENCE */ .ts_rdtsc32 = rdtsc32_mb_lfence, + .ts_rdtsc = rdtsc_mb_lfence, .ts_rdtsc_low = rdtsc_low_mb_lfence, }, [1] = { /* AMD, MFENCE */ .ts_rdtsc32 = rdtsc32_mb_mfence, + .ts_rdtsc = rdtsc_mb_mfence, .ts_rdtsc_low = rdtsc_low_mb_mfence, }, [2] = { /* No SSE2 */ - .ts_rdtsc32 = rdtsc32_mb_none, - .ts_rdtsc_low = rdtsc_low_mb_none, + .ts_rdtsc32 = rdtsc32_mb_none, + .ts_rdtsc = rdtsc_mb_none, + .ts_rdtsc_low = rdtsc_low_mb_none, }, [3] = { /* RDTSCP */ .ts_rdtsc32 = rdtscp32_, + .ts_rdtsc = rdtscp_, .ts_rdtsc_low = rdtscp_low, }, }; @@ -193,6 +224,11 @@ DEFINE_UIFUNC(static, u_int, __vdso_gettc_rdtsc32, (void)) return (tsc_selector[tsc_selector_idx(cpu_feature)].ts_rdtsc32); } +DEFINE_UIFUNC(static, uint64_t, __vdso_gettc_rdtsc, (void)) +{ + return (tsc_selector[tsc_selector_idx(cpu_feature)].ts_rdtsc); +} + #define HPET_DEV_MAP_MAX 10 static volatile char *hpet_dev_map[HPET_DEV_MAP_MAX]; @@ -325,7 +361,7 @@ __vdso_pvclock_gettc(const struct vdso_timehands *th, u_int *tc) version = atomic_load_acq_32(&ti->version); stable = (ti->flags & th->th_x86_pvc_stable_mask) != 0; if (stable) { - tsc = rdtscp(); + tsc = __vdso_gettc_rdtsc(); } else { (void)rdtscp_aux(&cpuid_ti); ti = &pvclock_timeinfos[cpuid_ti];
