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Sat, 04 Jul 2020 23:40:57 -0700 (PDT) Date: Sat, 4 Jul 2020 23:40:55 -0700 From: Andrei Vagin To: Catalin Marinas , Will Deacon Subject: Re: [PATCH v5 0/6] arm64: add the time namespace support Message-ID: <20200705064055.GA28894@gmail.com> References: <20200624083321.144975-1-avagin@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200624083321.144975-1-avagin@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200705_024101_419712_4B470D61 X-CRM114-Status: GOOD ( 21.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Dmitry Safonov , linux-kernel@vger.kernel.org, Thomas Gleixner , Vincenzo Frascino , Christian Brauner , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 24, 2020 at 01:33:15AM -0700, 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. > v4: - fix an issue reported by the lkp robot. > - vvar has the same size with/without CONFIG_TIME_NAMESPACE, but the > timens page isn't allocated on !CONFIG_TIME_NAMESPACE. This > simplifies criu/vdso migration between different kernel configs. > v5: - Code cleanups suggested by Mark Rutland. > - In vdso_join_timens, mmap_write_lock is downgraded to > mmap_read_lock. The VMA list isn't changed there, zap_page_range > doesn't require mmap_write_lock. > > Reviewed-by: Vincenzo Frascino > Reviewed-by: Dmitry Safonov Hello Will and Catalin, Have you had a chance to look at this patch set? I think it is ready to be merged. Let me know if you have any questions. Thanks, Andrei _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel