From: Andrei Vagin <avagin@gmail.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Dmitry Safonov <dima@arista.com>
Subject: Re: [PATCH 0/5] arm64: add the time namespace support
Date: Sun, 23 Feb 2020 00:08:11 -0800 [thread overview]
Message-ID: <20200223080811.GA349924@gmail.com> (raw)
In-Reply-To: <2d982452-12e5-5c0b-6e4c-adadb7a34616@arm.com>
On Thu, Feb 20, 2020 at 12:40:47PM +0000, Vincenzo Frascino wrote:
> Hi Andrei,
>
> On 04/02/2020 17:59, 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.
> >
>
> Thank you for adding the arm64 support of time namespaces. Overall it looks fine
> to me even if I have few comments. I will test it in the coming days just to
> make sure I did not miss something major. I will keep you updated on the results.
Thank you for the review. All comments look reasonable and I will
address them and post a second version.
Thanks,
Andrei
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prev parent reply other threads:[~2020-02-23 8:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 17:59 [PATCH 0/5] arm64: add the time namespace support Andrei Vagin
2020-02-04 17:59 ` [PATCH 1/5] arm64/vdso: use the fault callback to map vvar pages Andrei Vagin
2020-02-20 12:36 ` Vincenzo Frascino
2020-02-04 17:59 ` [PATCH 2/5] arm64/vdso: Zap vvar pages when switching to a time namespace Andrei Vagin
2020-02-04 17:59 ` [PATCH 3/5] arm64/vdso: Add time napespace page Andrei Vagin
2020-02-20 12:03 ` Vincenzo Frascino
2020-02-04 17:59 ` [PATCH 4/5] arm64/vdso: Handle faults on timens page Andrei Vagin
2020-02-20 12:07 ` Vincenzo Frascino
2020-02-04 17:59 ` [PATCH 5/5] arm64/vdso: Restrict splitting VVAR VMA Andrei Vagin
2020-02-20 12:22 ` Vincenzo Frascino
2020-02-23 23:30 ` Andrei Vagin
2020-02-24 10:08 ` Vincenzo Frascino
2020-02-17 15:34 ` [PATCH 0/5] arm64: add the time namespace support Andrei Vagin
2020-02-17 18:25 ` Vincenzo Frascino
2020-02-20 12:40 ` Vincenzo Frascino
2020-02-23 8:08 ` Andrei Vagin [this message]
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