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3aed64f6d3
The version field in struct pvclock_vcpu_time_info basically implements a seqcount. Wrap it with the usual read_begin and read_retry functions, and use these APIs instead of peppering the code with smp_rmb()s. While at it, change it to the more pedantically correct virt_rmb(). With this change, __pvclock_read_cycles can be simplified noticeably. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
105 lines
2.5 KiB
C
105 lines
2.5 KiB
C
#ifndef _ASM_X86_PVCLOCK_H
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#define _ASM_X86_PVCLOCK_H
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#include <linux/clocksource.h>
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#include <asm/pvclock-abi.h>
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#ifdef CONFIG_KVM_GUEST
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extern struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
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#else
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static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
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{
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return NULL;
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}
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#endif
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/* some helper functions for xen and kvm pv clock sources */
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cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
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u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
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void pvclock_set_flags(u8 flags);
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unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
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void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
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struct pvclock_vcpu_time_info *vcpu,
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struct timespec *ts);
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void pvclock_resume(void);
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void pvclock_touch_watchdogs(void);
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static __always_inline
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unsigned pvclock_read_begin(const struct pvclock_vcpu_time_info *src)
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{
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unsigned version = src->version & ~1;
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/* Make sure that the version is read before the data. */
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virt_rmb();
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return version;
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}
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static __always_inline
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bool pvclock_read_retry(const struct pvclock_vcpu_time_info *src,
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unsigned version)
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{
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/* Make sure that the version is re-read after the data. */
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virt_rmb();
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return unlikely(version != src->version);
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}
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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 u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
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{
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u64 product;
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#ifdef __i386__
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u32 tmp1, tmp2;
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#else
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ulong tmp;
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#endif
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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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#ifdef __i386__
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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" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
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#elif defined(__x86_64__)
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__asm__ (
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"mulq %[mul_frac] ; shrd $32, %[hi], %[lo]"
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: [lo]"=a"(product),
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[hi]"=d"(tmp)
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: "0"(delta),
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[mul_frac]"rm"((u64)mul_frac));
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#else
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#error implement me!
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#endif
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return product;
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}
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static __always_inline
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cycle_t __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src)
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{
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u64 delta = rdtsc_ordered() - src->tsc_timestamp;
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cycle_t offset = pvclock_scale_delta(delta, src->tsc_to_system_mul,
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src->tsc_shift);
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return src->system_time + offset;
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}
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struct pvclock_vsyscall_time_info {
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struct pvclock_vcpu_time_info pvti;
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} __attribute__((__aligned__(SMP_CACHE_BYTES)));
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#define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)
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#endif /* _ASM_X86_PVCLOCK_H */
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