Re: [PATCH 0/5] arm64: add the time namespace support
From: Andrei Vagin
Date: Mon Feb 17 2020 - 10:34:06 EST
Vincenzo, could you take a look this patchset?
On Tue, Feb 04, 2020 at 09:59:08AM -0800, 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.
> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Dmitry Safonov <dima@xxxxxxxxxx>
> Andrei Vagin (5):
> 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
> 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(-)