On Mon, Sep 22, 2014 at 04:39:19PM +0100, Will Deacon wrote: > On Thu, Sep 18, 2014 at 03:59:32PM +0100, Nathan Lynch wrote: > > This series contains the necessary changes to allow architected timer > > access from user-space on 32-bit ARM. This allows the VDSO to support > > high resolution timestamps for clock_gettime and gettimeofday. This > > also merges substantially similar code from arm and arm64 into the > > core arm_arch_timer driver. > > > > The functional changes are: > > - When available, CNTVCT is made readable by user space on arm, as it > > is on arm64. > > - The clocksource name becomes "arch_mem_counter" if CP15 access to > > the counter is not available. > > > > These changes have been carried as part of the ARM VDSO patch set over > > the last several months, but I am splitting them out here as I assume > > they should go through the clocksource maintainers. > > For the series: > > Acked-by: Will Deacon <will.dea...@arm.com> > > I'm not sure which tree the arch-timer stuff usually goes through, but > the arm/arm64 bits look fine so I'm happy for them to merged together.
I raised a while back with Will whether there's much point to having this on ARM. While it's useful for virtualisation, the majority of 32-bit ARM doesn't run virtualised. So there's little point in having the VDSO on the majority of platforms - it will just add additional unnecessary cycles slowing down the system calls that the VDSO is designed to try to speed up. So, my view is that this VDSO will only be of very limited use for 32-bit ARM, and should not be exposed to userspace unless there is a reason for it to be exposed (iow, the hardware necessary to support it is present.) -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
