From 638a9e433ecd61e64761352dbec1fa4f5874c941 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 7 Aug 2024 15:18:06 +0200 Subject: Merging upstream version 6.10.3. Signed-off-by: Daniel Baumann --- arch/x86/include/asm/vdso/gettimeofday.h | 44 ++++++++++++++++++++------------ 1 file changed, 28 insertions(+), 16 deletions(-) (limited to 'arch/x86/include/asm/vdso/gettimeofday.h') diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h index 8e048ca980..0ef36190ab 100644 --- a/arch/x86/include/asm/vdso/gettimeofday.h +++ b/arch/x86/include/asm/vdso/gettimeofday.h @@ -300,7 +300,7 @@ static inline bool arch_vdso_cycles_ok(u64 cycles) #define vdso_cycles_ok arch_vdso_cycles_ok /* - * x86 specific delta calculation. + * x86 specific calculation of nanoseconds for the current cycle count * * The regular implementation assumes that clocksource reads are globally * monotonic. The TSC can be slightly off across sockets which can cause @@ -308,8 +308,8 @@ static inline bool arch_vdso_cycles_ok(u64 cycles) * jump. * * Therefore it needs to be verified that @cycles are greater than - * @last. If not then use @last, which is the base time of the current - * conversion period. + * @vd->cycles_last. If not then use @vd->cycles_last, which is the base + * time of the current conversion period. * * This variant also uses a custom mask because while the clocksource mask of * all the VDSO capable clocksources on x86 is U64_MAX, the above code uses @@ -317,25 +317,37 @@ static inline bool arch_vdso_cycles_ok(u64 cycles) * declares everything with the MSB/Sign-bit set as invalid. Therefore the * effective mask is S64_MAX. */ -static __always_inline -u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult) +static __always_inline u64 vdso_calc_ns(const struct vdso_data *vd, u64 cycles, u64 base) { - /* - * Due to the MSB/Sign-bit being used as invalid marker (see - * arch_vdso_cycles_valid() above), the effective mask is S64_MAX. - */ - u64 delta = (cycles - last) & S64_MAX; + u64 delta = cycles - vd->cycle_last; /* - * Due to the above mentioned TSC wobbles, filter out negative motion. - * Per the above masking, the effective sign bit is now bit 62. + * Negative motion and deltas which can cause multiplication + * overflow require special treatment. This check covers both as + * negative motion is guaranteed to be greater than @vd::max_cycles + * due to unsigned comparison. + * + * Due to the MSB/Sign-bit being used as invalid marker (see + * arch_vdso_cycles_valid() above), the effective mask is S64_MAX, + * but that case is also unlikely and will also take the unlikely path + * here. */ - if (unlikely(delta & (1ULL << 62))) - return 0; + if (unlikely(delta > vd->max_cycles)) { + /* + * Due to the above mentioned TSC wobbles, filter out + * negative motion. Per the above masking, the effective + * sign bit is now bit 62. + */ + if (delta & (1ULL << 62)) + return base >> vd->shift; + + /* Handle multiplication overflow gracefully */ + return mul_u64_u32_add_u64_shr(delta & S64_MAX, vd->mult, base, vd->shift); + } - return delta * mult; + return ((delta * vd->mult) + base) >> vd->shift; } -#define vdso_calc_delta vdso_calc_delta +#define vdso_calc_ns vdso_calc_ns #endif /* !__ASSEMBLY__ */ -- cgit v1.2.3