Re: New kernel interface for sys_tz and timewarp?

Arnd Bergmann
2019-08-15T13:23:03Z

On Wed, Aug 14, 2019 at 6:48 PM <hpa@zytor.com> wrote:
>
> I believe Windows 10 changed the default RTC to UTC, although perhaps
> only if running under UEFI.

I looked at the efi rtc driver now, and found two things:

- The EFI get_time() call passes down timezone information, so we know what
UTC is, and can just ignore the timezone. This is good.

- The RTC_DRV_EFI depends on !X86 as of commit 7efe665903d0 ("rtc:
Disable EFI rtc for x86"). This unfortunately means we always fall back to
either the rtc-cmos driver or the x86 specific read_persistent_clock64()
implementation even when the EFI RTC is reliable.

If 64-bit Windows relies on a working EFI RTC implementation, we could
decide to leave the driver enabled on 64-bit and only disable it for
32-bit EFI. That way, future distros would no longer have to worry about
the localtime hack, at least the ones that have dropped support for
32-bit x86 kernels.

Arnd