From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8EE9C2BA19 for ; Tue, 14 Apr 2020 17:20:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EDB1206A2 for ; Tue, 14 Apr 2020 17:20:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407614AbgDNRU1 (ORCPT ); Tue, 14 Apr 2020 13:20:27 -0400 Received: from foss.arm.com ([217.140.110.172]:60396 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407594AbgDNRUY (ORCPT ); Tue, 14 Apr 2020 13:20:24 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C014430E; Tue, 14 Apr 2020 10:20:23 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.30.4]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 38E863F6C4; Tue, 14 Apr 2020 10:20:22 -0700 (PDT) Date: Tue, 14 Apr 2020 18:20:14 +0100 From: Mark Rutland To: Andrei Vagin Cc: Vincenzo Frascino , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Dmitry Safonov Subject: Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page Message-ID: <20200414172014.GA6705@C02TD0UTHF1T.local> References: <20200225073731.465270-1-avagin@gmail.com> <20200225073731.465270-4-avagin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200225073731.465270-4-avagin@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 24, 2020 at 11:37:28PM -0800, Andrei Vagin wrote: > Allocate the time namespace page among VVAR pages. Provide > __arch_get_timens_vdso_data() helper for VDSO code to get the > code-relative position of VVARs on that special page. > > 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. > > Signed-off-by: Andrei Vagin > --- > arch/arm64/include/asm/vdso.h | 6 ++++++ > .../include/asm/vdso/compat_gettimeofday.h | 11 ++++++++++ > arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++++++++ > arch/arm64/kernel/vdso.c | 20 ++++++++++++++++--- > arch/arm64/kernel/vdso/vdso.lds.S | 5 ++++- > arch/arm64/kernel/vdso32/vdso.lds.S | 5 ++++- > include/vdso/datapage.h | 1 + > 7 files changed, 51 insertions(+), 5 deletions(-) > +#ifdef CONFIG_TIME_NS > +static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void) > +{ > + const struct vdso_data *ret; > + > + asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data)); > + > + return ret; > +} > +#endif What is this inline assembly for? The commit message doesn't mention it, there's no explanation here, and the native version doesn't do likewise so it seems rather surprising. Thanks, Mark. > diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h > index 5a534432aa5d..553bdc19a91f 100644 > --- a/arch/arm64/include/asm/vdso/gettimeofday.h > +++ b/arch/arm64/include/asm/vdso/gettimeofday.h > @@ -97,6 +97,14 @@ const struct vdso_data *__arch_get_vdso_data(void) > return _vdso_data; > } > > +#ifdef CONFIG_TIME_NS > +static __always_inline > +const struct vdso_data *__arch_get_timens_vdso_data(void) > +{ > + return _timens_data; > +} > +#endif From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60208C2BA19 for ; Tue, 14 Apr 2020 17:20:32 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2D2A1206A2 for ; Tue, 14 Apr 2020 17:20:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="d2TIWBxD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D2A1206A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=GgDneSaqNKqf0jYMeoc4F6CVAqFk6gUr9HZ3R07ADwA=; b=d2TIWBxDjSsNW7 dBE+ApI5MoPcDaw5R2WWMavmrA9XKar/Nv5zJk9jEdRRHqrPI5ui81acbPEutX4EwjAV28RvOcHw0 gnO2pa7pqaXTmhp2v71F1WMVtIlE9sn6WPalsgz7DRM7kxFcu9EjwIpzcGPsU4w9aiexsYOh9NaP7 6ItY0rURxeBLx0Kk4CMBc/84jr6WiPM6dk5/g/J0Ii6V73+CP9NhkZW/30EmCI1gUSFRmi107Tvba myqmvRw3HGwIo8KMOLGN3MS5SrapuUzSUWyaFNOBni5NYgtkmGul6rlmTHiVBy+oFdefFV0w/6EqN iOMHFoZr4QUrGwTfwm4A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOPEa-00056r-C7; Tue, 14 Apr 2020 17:20:28 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOPEW-00054p-KG for linux-arm-kernel@lists.infradead.org; Tue, 14 Apr 2020 17:20:26 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C014430E; Tue, 14 Apr 2020 10:20:23 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.30.4]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 38E863F6C4; Tue, 14 Apr 2020 10:20:22 -0700 (PDT) Date: Tue, 14 Apr 2020 18:20:14 +0100 From: Mark Rutland To: Andrei Vagin Subject: Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page Message-ID: <20200414172014.GA6705@C02TD0UTHF1T.local> References: <20200225073731.465270-1-avagin@gmail.com> <20200225073731.465270-4-avagin@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200225073731.465270-4-avagin@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200414_102024_706024_79F7BFD8 X-CRM114-Status: GOOD ( 21.79 ) 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: Thomas Gleixner , Vincenzo Frascino , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Dmitry Safonov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Feb 24, 2020 at 11:37:28PM -0800, Andrei Vagin wrote: > Allocate the time namespace page among VVAR pages. Provide > __arch_get_timens_vdso_data() helper for VDSO code to get the > code-relative position of VVARs on that special page. > > 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. > > Signed-off-by: Andrei Vagin > --- > arch/arm64/include/asm/vdso.h | 6 ++++++ > .../include/asm/vdso/compat_gettimeofday.h | 11 ++++++++++ > arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++++++++ > arch/arm64/kernel/vdso.c | 20 ++++++++++++++++--- > arch/arm64/kernel/vdso/vdso.lds.S | 5 ++++- > arch/arm64/kernel/vdso32/vdso.lds.S | 5 ++++- > include/vdso/datapage.h | 1 + > 7 files changed, 51 insertions(+), 5 deletions(-) > +#ifdef CONFIG_TIME_NS > +static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void) > +{ > + const struct vdso_data *ret; > + > + asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data)); > + > + return ret; > +} > +#endif What is this inline assembly for? The commit message doesn't mention it, there's no explanation here, and the native version doesn't do likewise so it seems rather surprising. Thanks, Mark. > diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h > index 5a534432aa5d..553bdc19a91f 100644 > --- a/arch/arm64/include/asm/vdso/gettimeofday.h > +++ b/arch/arm64/include/asm/vdso/gettimeofday.h > @@ -97,6 +97,14 @@ const struct vdso_data *__arch_get_vdso_data(void) > return _vdso_data; > } > > +#ifdef CONFIG_TIME_NS > +static __always_inline > +const struct vdso_data *__arch_get_timens_vdso_data(void) > +{ > + return _timens_data; > +} > +#endif _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel