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    Subject[PATCH v2 02/17] x86/msr/kvm: Remove vget_cycles()
    Date
    The only caller was kvm's read_tsc.  The only difference between
    vget_cycles and native_read_tsc was that vget_cycles returned zero
    instead of crashing on TSC-less systems. KVM's already checks
    vclock_mode before calling that function, so the extra check is
    unnecessary.

    (Off-topic, but the whole KVM clock host implementation is gross.
    IMO it should be rewritten.)

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    ---
    arch/x86/include/asm/tsc.h | 13 -------------
    arch/x86/kvm/x86.c | 2 +-
    2 files changed, 1 insertion(+), 14 deletions(-)

    diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
    index fd11128faf25..3da1cc1218ac 100644
    --- a/arch/x86/include/asm/tsc.h
    +++ b/arch/x86/include/asm/tsc.h
    @@ -32,19 +32,6 @@ static inline cycles_t get_cycles(void)
    return ret;
    }

    -static __always_inline cycles_t vget_cycles(void)
    -{
    - /*
    - * We only do VDSOs on TSC capable CPUs, so this shouldn't
    - * access boot_cpu_data (which is not VDSO-safe):
    - */
    -#ifndef CONFIG_X86_TSC
    - if (!cpu_has_tsc)
    - return 0;
    -#endif
    - return (cycles_t)native_read_tsc();
    -}
    -
    extern void tsc_init(void);
    extern void mark_tsc_unstable(char *reason);
    extern int unsynchronized_tsc(void);
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 26eaeb522cab..c26faf408bce 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -1430,7 +1430,7 @@ static cycle_t read_tsc(void)
    * but no one has ever seen it happen.
    */
    rdtsc_barrier();
    - ret = (cycle_t)vget_cycles();
    + ret = (cycle_t)native_read_tsc();

    last = pvclock_gtod_data.clock.cycle_last;

    --
    2.4.2


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