324 lines
8.1 KiB
C
324 lines
8.1 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Fast user context implementation of clock_gettime, gettimeofday, and time.
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*
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* Copyright (C) 2019 ARM Limited.
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* Copyright 2006 Andi Kleen, SUSE Labs.
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* 32 Bit compat layer by Stefani Seibold <stefani@seibold.net>
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* sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
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*/
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#ifndef __ASM_VDSO_GETTIMEOFDAY_H
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#define __ASM_VDSO_GETTIMEOFDAY_H
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#ifndef __ASSEMBLY__
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#include <uapi/linux/time.h>
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#include <asm/vgtod.h>
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#include <asm/vvar.h>
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#include <asm/unistd.h>
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#include <asm/msr.h>
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#include <asm/pvclock.h>
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#include <clocksource/hyperv_timer.h>
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#define __vdso_data (VVAR(_vdso_data))
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#define __timens_vdso_data (TIMENS(_vdso_data))
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#define VDSO_HAS_TIME 1
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#define VDSO_HAS_CLOCK_GETRES 1
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/*
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* Declare the memory-mapped vclock data pages. These come from hypervisors.
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* If we ever reintroduce something like direct access to an MMIO clock like
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* the HPET again, it will go here as well.
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*
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* A load from any of these pages will segfault if the clock in question is
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* disabled, so appropriate compiler barriers and checks need to be used
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* to prevent stray loads.
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*
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* These declarations MUST NOT be const. The compiler will assume that
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* an extern const variable has genuinely constant contents, and the
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* resulting code won't work, since the whole point is that these pages
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* change over time, possibly while we're accessing them.
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*/
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#ifdef CONFIG_PARAVIRT_CLOCK
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/*
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* This is the vCPU 0 pvclock page. We only use pvclock from the vDSO
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* if the hypervisor tells us that all vCPUs can get valid data from the
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* vCPU 0 page.
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*/
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extern struct pvclock_vsyscall_time_info pvclock_page
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__attribute__((visibility("hidden")));
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#endif
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#ifdef CONFIG_HYPERV_TIMER
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extern struct ms_hyperv_tsc_page hvclock_page
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__attribute__((visibility("hidden")));
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#endif
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#ifdef CONFIG_TIME_NS
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static __always_inline
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const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)
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{
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return __timens_vdso_data;
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}
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#endif
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#ifndef BUILD_VDSO32
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static __always_inline
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long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
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{
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long ret;
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asm ("syscall" : "=a" (ret), "=m" (*_ts) :
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"0" (__NR_clock_gettime), "D" (_clkid), "S" (_ts) :
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"rcx", "r11");
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return ret;
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}
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static __always_inline
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long gettimeofday_fallback(struct __kernel_old_timeval *_tv,
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struct timezone *_tz)
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{
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long ret;
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asm("syscall" : "=a" (ret) :
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"0" (__NR_gettimeofday), "D" (_tv), "S" (_tz) : "memory");
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return ret;
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}
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static __always_inline
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long clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
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{
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long ret;
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asm ("syscall" : "=a" (ret), "=m" (*_ts) :
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"0" (__NR_clock_getres), "D" (_clkid), "S" (_ts) :
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"rcx", "r11");
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return ret;
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}
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#else
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static __always_inline
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long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
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{
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long ret;
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asm (
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"mov %%ebx, %%edx \n"
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"mov %[clock], %%ebx \n"
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"call __kernel_vsyscall \n"
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"mov %%edx, %%ebx \n"
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: "=a" (ret), "=m" (*_ts)
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: "0" (__NR_clock_gettime64), [clock] "g" (_clkid), "c" (_ts)
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: "edx");
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return ret;
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}
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static __always_inline
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long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
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{
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long ret;
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asm (
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"mov %%ebx, %%edx \n"
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"mov %[clock], %%ebx \n"
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"call __kernel_vsyscall \n"
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"mov %%edx, %%ebx \n"
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: "=a" (ret), "=m" (*_ts)
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: "0" (__NR_clock_gettime), [clock] "g" (_clkid), "c" (_ts)
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: "edx");
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return ret;
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}
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static __always_inline
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long gettimeofday_fallback(struct __kernel_old_timeval *_tv,
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struct timezone *_tz)
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{
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long ret;
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asm(
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"mov %%ebx, %%edx \n"
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"mov %2, %%ebx \n"
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"call __kernel_vsyscall \n"
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"mov %%edx, %%ebx \n"
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: "=a" (ret)
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: "0" (__NR_gettimeofday), "g" (_tv), "c" (_tz)
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: "memory", "edx");
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return ret;
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}
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static __always_inline long
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clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
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{
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long ret;
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asm (
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"mov %%ebx, %%edx \n"
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"mov %[clock], %%ebx \n"
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"call __kernel_vsyscall \n"
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"mov %%edx, %%ebx \n"
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: "=a" (ret), "=m" (*_ts)
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: "0" (__NR_clock_getres_time64), [clock] "g" (_clkid), "c" (_ts)
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: "edx");
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return ret;
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}
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static __always_inline
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long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
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{
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long ret;
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asm (
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"mov %%ebx, %%edx \n"
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"mov %[clock], %%ebx \n"
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"call __kernel_vsyscall \n"
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"mov %%edx, %%ebx \n"
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: "=a" (ret), "=m" (*_ts)
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: "0" (__NR_clock_getres), [clock] "g" (_clkid), "c" (_ts)
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: "edx");
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return ret;
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}
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#endif
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#ifdef CONFIG_PARAVIRT_CLOCK
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static u64 vread_pvclock(void)
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{
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const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti;
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u32 version;
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u64 ret;
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/*
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* Note: The kernel and hypervisor must guarantee that cpu ID
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* number maps 1:1 to per-CPU pvclock time info.
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*
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* Because the hypervisor is entirely unaware of guest userspace
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* preemption, it cannot guarantee that per-CPU pvclock time
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* info is updated if the underlying CPU changes or that that
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* version is increased whenever underlying CPU changes.
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*
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* On KVM, we are guaranteed that pvti updates for any vCPU are
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* atomic as seen by *all* vCPUs. This is an even stronger
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* guarantee than we get with a normal seqlock.
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*
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* On Xen, we don't appear to have that guarantee, but Xen still
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* supplies a valid seqlock using the version field.
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*
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* We only do pvclock vdso timing at all if
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* PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to
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* mean that all vCPUs have matching pvti and that the TSC is
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* synced, so we can just look at vCPU 0's pvti.
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*/
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do {
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version = pvclock_read_begin(pvti);
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if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT)))
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return U64_MAX;
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ret = __pvclock_read_cycles(pvti, rdtsc_ordered());
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} while (pvclock_read_retry(pvti, version));
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return ret;
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}
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#endif
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#ifdef CONFIG_HYPERV_TIMER
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static u64 vread_hvclock(void)
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{
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return hv_read_tsc_page(&hvclock_page);
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}
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#endif
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static inline u64 __arch_get_hw_counter(s32 clock_mode,
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const struct vdso_data *vd)
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{
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if (likely(clock_mode == VDSO_CLOCKMODE_TSC))
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return (u64)rdtsc_ordered();
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/*
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* For any memory-mapped vclock type, we need to make sure that gcc
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* doesn't cleverly hoist a load before the mode check. Otherwise we
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* might end up touching the memory-mapped page even if the vclock in
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* question isn't enabled, which will segfault. Hence the barriers.
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*/
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#ifdef CONFIG_PARAVIRT_CLOCK
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if (clock_mode == VDSO_CLOCKMODE_PVCLOCK) {
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barrier();
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return vread_pvclock();
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}
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#endif
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#ifdef CONFIG_HYPERV_TIMER
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if (clock_mode == VDSO_CLOCKMODE_HVCLOCK) {
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barrier();
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return vread_hvclock();
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}
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#endif
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return U64_MAX;
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}
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static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
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{
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return __vdso_data;
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}
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static inline bool arch_vdso_clocksource_ok(const struct vdso_data *vd)
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{
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return true;
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}
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#define vdso_clocksource_ok arch_vdso_clocksource_ok
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/*
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* Clocksource read value validation to handle PV and HyperV clocksources
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* which can be invalidated asynchronously and indicate invalidation by
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* returning U64_MAX, which can be effectively tested by checking for a
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* negative value after casting it to s64.
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*/
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static inline bool arch_vdso_cycles_ok(u64 cycles)
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{
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return (s64)cycles >= 0;
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}
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#define vdso_cycles_ok arch_vdso_cycles_ok
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/*
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* x86 specific delta calculation.
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*
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* The regular implementation assumes that clocksource reads are globally
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* monotonic. The TSC can be slightly off across sockets which can cause
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* the regular delta calculation (@cycles - @last) to return a huge time
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* jump.
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*
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* Therefore it needs to be verified that @cycles are greater than
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* @last. If not then use @last, which is the base time of the current
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* conversion period.
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*
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* This variant also removes the masking of the subtraction because the
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* clocksource mask of all VDSO capable clocksources on x86 is U64_MAX
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* which would result in a pointless operation. The compiler cannot
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* optimize it away as the mask comes from the vdso data and is not compile
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* time constant.
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*/
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static __always_inline
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u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
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{
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if (cycles > last)
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return (cycles - last) * mult;
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return 0;
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}
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#define vdso_calc_delta vdso_calc_delta
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#endif /* !__ASSEMBLY__ */
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#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
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