On Fri, Oct 13, 2017 at 10:45 PM, Boris Ostrovsky
<boris.ostrovsky@xxxxxxxxxx> wrote:
> On 10/13/2017 02:37 PM, 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.
>>
>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>> ---
>> 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 | 6 +++---
>> arch/x86/kernel/kvmclock.c | 4 ++--
>> arch/x86/kernel/pvclock.c | 12 +++++++++---
>> arch/x86/kernel/rtc.c | 16 ++++++++--------
>> arch/x86/platform/intel-mid/intel_mid_vrtc.c | 10 +++++-----
>> arch/x86/xen/time.c | 10 +++++-----
>> 9 files changed, 37 insertions(+), 31 deletions(-)
>
> Xen bits:
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Thanks!
Since you've looked at it overall, do you have an opinion on the question
how to fix the PV interface to deal with the pvclock_wall_clock overflow?
Should we add a new version now and deprecate the existing one, or
do you think that y2106 is far enough out that we should just ignore the
problem?
> with a couple of nits:
>
>> @@ -136,11 +136,17 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
>> rmb(); /* fetch time before checking version */
>> } while ((wall_clock->version & 1) || (version != wall_clock->version));
>>
>> + /*
>> + * 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.
>> + */
>
> I think this comment block should be moved up above 'now.tv_sec =
> wall_clock->sec;'
right, changed.
>> delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
>> delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
>
> Now that tv_sec is a 64-bit quantity the cast can be dropped.
Ok dropped. In the meantime I had noticed two more problems with the
patch that I did not see earlier when I tested with another patch applied
as well. The kbuild test robot reported the exact same problems, and I've
done a few hundred randconfig builds without the other patch now, so
I'm fairly confident that there are no other problems like those.
I'll follow up with a v2 patch soon.
Arnd
