Re: [Xen-devel] [PATCH] [v3] x86: Convert x86_platform_ops to timespec64

[Radim Krčmář <rkrcmar@xxxxxxxxxx>]

2018-04-27 22:13+0200, Arnd Bergmann:
> The x86 platform operations are fairly isolated, so we can
> change them from using timespec to timespec64. I checked that
> All the users and callers are safe, and there is only one
> critical function that is broken beyond 2106:
> 
> pvclock_read_wallclock() uses a 32-bit number of seconds since
> the epoch to communicate the boot time between host and guest
> in a virtual environment. This will work until 2106, but we
> should ideally find a replacement anyway. I've added a comment
> about it there.
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> v2 changes:
> - move comment block (Boris)
> - remove unnecessary type cast (Boris)
> - fix format string (0day bot)
> - fix include order (0day bot)
> 
> v3 changes:
> - add jailhouse specific change
> - avoid include file header by relying on another
>   patch ("timekeeping: Remove timespec64 hack")
> 
> Not sure how we want to merge this (assuming the last modification
> worked, this has seen little testing). The "timekeeping: Remove
> timespec64 hack" patch should go through the timekeeping branch
> in tip, while this one is for x86. I assume the linux-tip maintainers
> can come up with a plan.
> ---
> diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
> @@ -12,7 +12,7 @@ void pvclock_set_flags(u8 flags);
>  unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
>  void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
>                           struct pvclock_vcpu_time_info *vcpu,
> -                         struct timespec *ts);
> +                         struct timespec64 *ts);
>  void pvclock_resume(void);
>  
>  void pvclock_touch_watchdogs(void);
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> @@ -53,7 +53,7 @@ static struct pvclock_wall_clock *wall_clock;
>   * have elapsed since the hypervisor wrote the data. So we try to account for
>   * that with system time
>   */
> -static void kvm_get_wallclock(struct timespec *now)
> +static void kvm_get_wallclock(struct timespec64 *now)
>  {
>       struct pvclock_vcpu_time_info *vcpu_time;
>       int low, high;
> @@ -72,7 +72,7 @@ static void kvm_get_wallclock(struct timespec *now)
>       put_cpu();
>  }
>  
> -static int kvm_set_wallclock(const struct timespec *now)
> +static int kvm_set_wallclock(const struct timespec64 *now)
>  {
>       return -ENODEV;
>  }
> diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
> @@ -123,28 +123,35 @@ u64 pvclock_clocksource_read(struct 
> pvclock_vcpu_time_info *src)
>  
>  void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
>                           struct pvclock_vcpu_time_info *vcpu_time,
> -                         struct timespec *ts)
> +                         struct timespec64 *ts)
>  {
>       u32 version;
>       u64 delta;
> -     struct timespec now;
> +     struct timespec64 now;
>  
>       /* get wallclock at system boot */
>       do {
>               version = wall_clock->version;
>               rmb();          /* fetch version before time */
> +             /*
> +              * Note: wall_clock->sec is a u32 value, so it can
> +              * only store dates between 1970 and 2106. To allow
> +              * times beyond that, we need to create a new hypercall
> +              * interface with an extended pvclock_wall_clock structure
> +              * like ARM has.
> +              */

(Modern TSC extensions stripped pvclock of all advantages, so we'll
 likely abandon pvclock by then.)

>               now.tv_sec  = wall_clock->sec;
>               now.tv_nsec = wall_clock->nsec;
>               rmb();          /* fetch time before checking version */
>       } while ((wall_clock->version & 1) || (version != wall_clock->version));
>  
>       delta = pvclock_clocksource_read(vcpu_time);    /* time since system 
> boot */
> -     delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
> +     delta += now.tv_sec * NSEC_PER_SEC + now.tv_nsec;
>  
>       now.tv_nsec = do_div(delta, NSEC_PER_SEC);
>       now.tv_sec = delta;
>  
> -     set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
> +     set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec);
>  }
>  
>  void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)

kvmclock and pvclock changes

Acked-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>

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