Hi Andrei,
On 6/2/20 7:02 PM, Andrei Vagin wrote:
> Allocate the time namespace page among VVAR pages and add the logic
> to handle faults on VVAR properly.
>
> If a task belongs to a time namespace then the VVAR page which contains
> the system wide VDSO data is replaced with a namespace specific page
> which has the same layout as the VVAR page. That page has vdso_data->seq
> set to 1 to enforce the slow path and vdso_data->clock_mode set to
> VCLOCK_TIMENS to enforce the time namespace handling path.
>
> The extra check in the case that vdso_data->seq is odd, e.g. a concurrent
> update of the VDSO data is in progress, is not really affecting regular
> tasks which are not part of a time namespace as the task is spin waiting
> for the update to finish and vdso_data->seq to become even again.
>
> If a time namespace task hits that code path, it invokes the corresponding
> time getter function which retrieves the real VVAR page, reads host time
> and then adds the offset for the requested clock which is stored in the
> special VVAR page.
>
> v2: Code cleanups suggested by Vincenzo.
> v3: add a comment in __arch_get_timens_vdso_data.
>
> Reviewed-by: Vincenzo Frascino <vincenzo.frasc...@arm.com>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Dmitry Safonov <d...@arista.com>
>
> v3 on github (if someone prefers `git pull` to `git am`):
> https://github.com/avagin/linux-task-diag/tree/arm64/timens-v3
Thanks for adding arm64 support, I've looked through patches and don't
see any major problems.
Reviewed-by: Dmitry Safonov <d...@arista.com>
>
> Andrei Vagin (6):
> arm64/vdso: use the fault callback to map vvar pages
> arm64/vdso: Zap vvar pages when switching to a time namespace
> arm64/vdso: Add time napespace page
> arm64/vdso: Handle faults on timens page
> arm64/vdso: Restrict splitting VVAR VMA
> arm64: enable time namespace support
>
> arch/arm64/Kconfig | 1 +
> .../include/asm/vdso/compat_gettimeofday.h | 11 ++
> arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++
> arch/arm64/kernel/vdso.c | 134 ++++++++++++++++--
> arch/arm64/kernel/vdso/vdso.lds.S | 3 +-
> arch/arm64/kernel/vdso32/vdso.lds.S | 3 +-
> include/vdso/datapage.h | 1 +
> 7 files changed, 147 insertions(+), 14 deletions(-)
>
Thanks,
Dmitry
