linux-kernel - Re: [PATCH v2 2/2] x86: convert x86_platform

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Date:   Thu, 19 Oct 2017 13:46:50 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Cc:     y2038@...ts.linaro.org, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Marcos Paulo de Souza <marcos.souza.org@...il.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        John Stultz <john.stultz@...aro.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v2 2/2] x86: convert x86_platform_ops to timespec64

On 19/10/2017 12:57, Arnd Bergmann wrote:
> 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@...cle.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> v2 changes:
> - move comment block (Boris)
> - remove unnecessary type cast (Boris)
> - fix format string (0day bot)
> - fix include order (0day bot)
> ---
>  arch/x86/include/asm/intel_mid_vrtc.h        |  4 ++--
>  arch/x86/include/asm/mc146818rtc.h           |  4 ++--
>  arch/x86/include/asm/pvclock.h               |  2 +-
>  arch/x86/include/asm/x86_init.h              |  7 +++----
>  arch/x86/kernel/kvmclock.c                   |  4 ++--
>  arch/x86/kernel/pvclock.c                    | 15 +++++++++++----
>  arch/x86/kernel/rtc.c                        | 16 ++++++++--------
>  arch/x86/platform/intel-mid/intel_mid_vrtc.c | 12 ++++++------
>  arch/x86/xen/time.c                          | 10 +++++-----
>  9 files changed, 40 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index d88967659098..01c76e8cd4be 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -58,7 +58,7 @@ EXPORT_SYMBOL_GPL(pvclock_pvti_cpu0_va);
>   * 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;
> @@ -77,7 +77,7 @@ 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 -1;
>  }
> diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
> index 5c3f6d6a5078..013bef851664 100644
> --- a/arch/x86/kernel/pvclock.c
> +++ b/arch/x86/kernel/pvclock.c
> @@ -121,26 +121,33 @@ 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.
> +		 */
>  		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);
>  }
For kvmclock.c and pvclock.c,

Acked-by: Paolo Bonzini <pbonzini@...hat.com>