The branch stable/12 has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=2a16b0f333d47430c9d932aafa7d2af46f475fd4
commit 2a16b0f333d47430c9d932aafa7d2af46f475fd4 Author: Adam Fenn <[email protected]> AuthorDate: 2021-08-07 20:11:29 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2021-10-12 16:01:26 +0000 libc: vDSO timekeeping: Add pvclock support Add support for 'VDSO_TH_ALGO_X86_PVCLK'; add vDSO-based timekeeping for devices that support the KVM/XEN paravirtual clock API. Sponsored by: Juniper Networks, Inc. Sponsored by: Klara, Inc. Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D31418 (cherry picked from commit a3d932dfef5edc9d1c947b02fb93a64d63a291cb) --- lib/libc/x86/sys/__vdso_gettc.c | 62 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/lib/libc/x86/sys/__vdso_gettc.c b/lib/libc/x86/sys/__vdso_gettc.c index 1f3e8133040f..303b2c4e771c 100644 --- a/lib/libc/x86/sys/__vdso_gettc.c +++ b/lib/libc/x86/sys/__vdso_gettc.c @@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$"); #include "un-namespace.h" #include <machine/atomic.h> #include <machine/cpufunc.h> +#include <machine/pvclock.h> #include <machine/specialreg.h> #include <dev/acpica/acpi_hpet.h> #ifdef WANT_HYPERV @@ -312,6 +313,61 @@ __vdso_hyperv_tsc(struct hyperv_reftsc *tsc_ref, u_int *tc) #endif /* WANT_HYPERV */ +static struct pvclock_vcpu_time_info *pvclock_timeinfos; + +static int +__vdso_pvclock_gettc(const struct vdso_timehands *th, u_int *tc) +{ + uint64_t delta, ns, tsc; + struct pvclock_vcpu_time_info *ti; + uint32_t cpuid_ti, cpuid_tsc, version; + bool stable; + + do { + ti = &pvclock_timeinfos[0]; + version = atomic_load_acq_32(&ti->version); + stable = (ti->flags & th->th_x86_pvc_stable_mask) != 0; + if (stable) { + tsc = rdtscp(); + } else { + (void)rdtscp_aux(&cpuid_ti); + ti = &pvclock_timeinfos[cpuid_ti]; + version = atomic_load_acq_32(&ti->version); + tsc = rdtscp_aux(&cpuid_tsc); + } + delta = tsc - ti->tsc_timestamp; + ns = ti->system_time + pvclock_scale_delta(delta, + ti->tsc_to_system_mul, ti->tsc_shift); + atomic_thread_fence_acq(); + } while ((ti->version & 1) != 0 || ti->version != version || + (!stable && cpuid_ti != cpuid_tsc)); + *tc = MAX(ns, th->th_x86_pvc_last_systime); + return (0); +} + +static void +__vdso_init_pvclock_timeinfos(void) +{ + struct pvclock_vcpu_time_info *timeinfos; + size_t len; + int fd, ncpus; + unsigned int mode; + + timeinfos = MAP_FAILED; + if (_elf_aux_info(AT_NCPUS, &ncpus, sizeof(ncpus)) != 0 || + (cap_getmode(&mode) == 0 && mode != 0) || + (fd = _open("/dev/" PVCLOCK_CDEVNAME, O_RDONLY | O_CLOEXEC)) < 0) + goto leave; + len = ncpus * sizeof(*pvclock_timeinfos); + timeinfos = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0); + _close(fd); +leave: + if (atomic_cmpset_rel_ptr( + (volatile uintptr_t *)&pvclock_timeinfos, (uintptr_t)NULL, + (uintptr_t)timeinfos) == 0 && timeinfos != MAP_FAILED) + (void)munmap((void *)timeinfos, len); +} + #pragma weak __vdso_gettc int __vdso_gettc(const struct vdso_timehands *th, u_int *tc) @@ -347,6 +403,12 @@ __vdso_gettc(const struct vdso_timehands *th, u_int *tc) return (ENOSYS); return (__vdso_hyperv_tsc(hyperv_ref_tsc, tc)); #endif + case VDSO_TH_ALGO_X86_PVCLK: + if (pvclock_timeinfos == NULL) + __vdso_init_pvclock_timeinfos(); + if (pvclock_timeinfos == MAP_FAILED) + return (ENOSYS); + return (__vdso_pvclock_gettc(th, tc)); default: return (ENOSYS); }
