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2bed14192c
When the cycle counter is "stable", i.e., synchronized across vCPUs by the hypervisor, userspace can use a serialized rdtsc instead of relying on rdtscp, just like the kernel timecounter does. This can be useful for performance in guests where the hypervisor hides rdtscp for some reason. To avoid breaking compatibility with older userspace which expects rdtscp to be usable when pvclock exports timekeeping info, hide this feature behind a sysctl. Reviewed by: kib Tested by: Shrikanth R Kamath <kshrikanth@juniper.net> MFC after: 2 weeks Sponsored by: Klara, Inc. Sponsored by: Juniper Networks, Inc. Differential Revision: https://reviews.freebsd.org/D38342
147 lines
4.1 KiB
C
147 lines
4.1 KiB
C
/*-
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* Copyright (c) 2014, Bryan Venteicher <bryanv@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef X86_PVCLOCK
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#define X86_PVCLOCK
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#include <sys/types.h>
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#ifdef _KERNEL
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#include <sys/timetc.h>
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#endif /* _KERNEL */
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#define PVCLOCK_CDEVNAME "pvclock"
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struct pvclock_vcpu_time_info {
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uint32_t version;
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uint32_t pad0;
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uint64_t tsc_timestamp;
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uint64_t system_time;
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uint32_t tsc_to_system_mul;
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int8_t tsc_shift;
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uint8_t flags;
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uint8_t pad[2];
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};
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#define PVCLOCK_FLAG_TSC_STABLE 0x01
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#define PVCLOCK_FLAG_GUEST_PASUED 0x02
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/*
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* Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
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* yielding a 64-bit result.
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*/
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static inline uint64_t
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pvclock_scale_delta(uint64_t delta, uint32_t mul_frac, int shift)
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{
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uint64_t product;
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if (shift < 0)
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delta >>= -shift;
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else
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delta <<= shift;
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#if defined(__i386__)
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{
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uint32_t tmp1, tmp2;
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/**
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* For i386, the formula looks like:
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*
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* lower = (mul_frac * (delta & UINT_MAX)) >> 32
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* upper = mul_frac * (delta >> 32)
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* product = lower + upper
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*/
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__asm__ (
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"mul %5 ; "
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"mov %4,%%eax ; "
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"mov %%edx,%4 ; "
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"mul %5 ; "
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"xor %5,%5 ; "
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"add %4,%%eax ; "
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"adc %5,%%edx ; "
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: "=A" (product), "=r" (tmp1), "=r" (tmp2)
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: "a" ((uint32_t)delta), "1" ((uint32_t)(delta >> 32)),
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"2" (mul_frac) );
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}
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#elif defined(__amd64__)
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{
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unsigned long tmp;
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__asm__ (
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"mulq %[mul_frac] ; shrd $32, %[hi], %[lo]"
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: [lo]"=a" (product), [hi]"=d" (tmp)
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: "0" (delta), [mul_frac]"rm"((uint64_t)mul_frac));
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}
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#else
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#error "pvclock: unsupported x86 architecture?"
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#endif
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return (product);
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}
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#ifdef _KERNEL
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typedef struct pvclock_wall_clock *pvclock_get_wallclock_t(void *arg);
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struct pvclock_wall_clock {
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uint32_t version;
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uint32_t sec;
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uint32_t nsec;
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};
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struct pvclock {
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/* Public; initialized by the caller of 'pvclock_init()': */
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pvclock_get_wallclock_t *get_wallclock;
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void *get_wallclock_arg;
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struct pvclock_vcpu_time_info *timeinfos;
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bool stable_flag_supported;
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/* Private; initialized by the 'pvclock' API: */
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bool vdso_force_unstable;
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bool vdso_enable_without_rdtscp;
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struct timecounter tc;
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struct cdev *cdev;
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};
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/*
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* NOTE: 'pvclock_get_timecount()' and 'pvclock_get_wallclock()' are purely
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* transitional; they should be removed after 'dev/xen/timer/timer.c' has been
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* migrated to the 'struct pvclock' API.
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*/
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void pvclock_resume(void);
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uint64_t pvclock_tsc_freq(struct pvclock_vcpu_time_info *ti);
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uint64_t pvclock_get_timecount(struct pvclock_vcpu_time_info *ti);
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void pvclock_get_wallclock(struct pvclock_wall_clock *wc,
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struct timespec *ts);
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void pvclock_init(struct pvclock *pvc, device_t dev,
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const char *tc_name, int tc_quality, u_int tc_flags);
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void pvclock_gettime(struct pvclock *pvc, struct timespec *ts);
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int pvclock_destroy(struct pvclock *pvc);
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#endif /* _KERNEL */
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#endif
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