From patchwork Tue Sep 19 19:01:57 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 13391771 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72916CE79AB for ; Tue, 19 Sep 2023 19:02:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DE4F36B00B5; Tue, 19 Sep 2023 15:02:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D96396B00B6; Tue, 19 Sep 2023 15:02:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C5E016B00B7; Tue, 19 Sep 2023 15:02:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id B87C86B00B5 for ; Tue, 19 Sep 2023 15:02:19 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 88FC5160DEA for ; Tue, 19 Sep 2023 19:02:19 +0000 (UTC) X-FDA: 81254267598.23.F580E10 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) by imf15.hostedemail.com (Postfix) with ESMTP id CC811A0036 for ; Tue, 19 Sep 2023 19:02:16 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=gikkBPOF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf15.hostedemail.com: domain of 3N_AJZQ0KCG4MjQXdMeYgeeQZSaaSXQ.OaYXUZgj-YYWhMOW.adS@flex--axelrasmussen.bounces.google.com designates 209.85.128.202 as permitted sender) smtp.mailfrom=3N_AJZQ0KCG4MjQXdMeYgeeQZSaaSXQ.OaYXUZgj-YYWhMOW.adS@flex--axelrasmussen.bounces.google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1695150136; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=OM7/ZBsweEHQQFPt50lI+eLlVKDaLR0lSsGnYD/uIDg=; b=ydXUpCkc7P+9/oz8YmzLCoPFT08t7E4uCO9AKwcbyLDY9dPDQxAD+mRsk/dhzDcV0dstIL 7qBjp/Lei+JrV7LnGlNK7qbvFnPUCAuEM1EyDqxgErV1OsLPcvJayb14eW4J/lru6BrOl1 UN6uUT3aAT7QNWCSxAj4MFYinswMpak= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=gikkBPOF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf15.hostedemail.com: domain of 3N_AJZQ0KCG4MjQXdMeYgeeQZSaaSXQ.OaYXUZgj-YYWhMOW.adS@flex--axelrasmussen.bounces.google.com designates 209.85.128.202 as permitted sender) smtp.mailfrom=3N_AJZQ0KCG4MjQXdMeYgeeQZSaaSXQ.OaYXUZgj-YYWhMOW.adS@flex--axelrasmussen.bounces.google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1695150136; a=rsa-sha256; cv=none; b=CgXxPMEwx9P0jRaLy8zkvv7ncYBydBEf2QPm1knz2USDrOZS0rSZfsaAPy0LQLq/k6NZm1 sscjbmSBI3KO2jeCmkADOA9rriyWxKsp6BAJigDotVfwdXa/3auT3+AfRacEGlfKw7fway c2DS1MoUY4YfhSOE3/uqSUWmGeBqVn4= Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-59c240e637aso48602977b3.3 for ; Tue, 19 Sep 2023 12:02:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695150136; x=1695754936; darn=kvack.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=OM7/ZBsweEHQQFPt50lI+eLlVKDaLR0lSsGnYD/uIDg=; b=gikkBPOFHF4nUNdXls6DWfsxajrFW3Oy4wsat8jeCBA/MZ4Zpa7ftfJ11aFpZLNMqj Ei7S51WgYN1Kllz2vdO/cuRiS5jU+UqDBqCPamTFPLo9f+EAUY16IBx5oj1rYyCd9gw/ QPQxJKKjn+6sWzZu13Sb0Dymt+BFpWGpQ4gjEWSS/PO8+Z9hiL7vOEi3V3AXs/Z+baEi g45Aa8iQUw0meS7uNDLuECvwjTOB4Ri7QujquTRRuVSGFmN0Nj/eDYbcjdDu5Mly2ny1 HlsHEFbe43vM7Jn6sM4MymZ7Cv+U9icfuqakrBLuHJRM98shDIV34C4ITu9m1BXShBME pWQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695150136; x=1695754936; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=OM7/ZBsweEHQQFPt50lI+eLlVKDaLR0lSsGnYD/uIDg=; b=Tai4cDYRLyeilhavy1dkGX+/+mVX3xQFt4SyDxIXJ07ZXgc2+tucFx/HaL0gb+/pW+ ctxViCr29DrLrM+XjENEECkJw9hkX3V11+1tR4dEbXOwPk3K8wuoNklUaMJ47wLXieKh I8GxA58xV/mENgyG6Fxe5zSVtZFFjVVxi1GX59LTcGgMY64mAMGs5L2zlTER4axUCa5B N3Hwvrey4gIoXNapgtTtUd/yBIj2k1UxbaVAgjgAQPrOT51dHU7x7Z0RznqLzf3uNV5T OOOrQXz/2l7uQZkvh3A0IbRszpvwzcGiZVno90XypPuD7OjpVmXQjPNFKHx3zGoJQOca 5Bvg== X-Gm-Message-State: AOJu0YwyQdow22I1hRDbP1zjTcxRkHOWVelgOfeRMPUCYZROqc9zw57M qVVS9E4i1poNN2ZxXFkG1SrePJylvdUSRTz1f2LR X-Google-Smtp-Source: AGHT+IFf0kRJIOcrKDJvGyy+9uuMetyVG0rmWrcYJuPzwTUle78T8JRLjh7ImzOta7b6zc579tMrz4KeWMgNFH3qWKPl X-Received: from axel.svl.corp.google.com ([2620:15c:2a3:200:8f5a:6a6a:cafc:a3ad]) (user=axelrasmussen job=sendgmr) by 2002:a25:ab48:0:b0:d81:68ac:e046 with SMTP id u66-20020a25ab48000000b00d8168ace046mr6411ybi.12.1695150135954; Tue, 19 Sep 2023 12:02:15 -0700 (PDT) Date: Tue, 19 Sep 2023 12:01:57 -0700 In-Reply-To: <20230919190206.388896-1-axelrasmussen@google.com> Mime-Version: 1.0 References: <20230919190206.388896-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.42.0.459.ge4e396fd5e-goog Message-ID: <20230919190206.388896-2-axelrasmussen@google.com> Subject: [PATCH 01/10] userfaultfd.2: briefly mention two-step feature handshake process From: Axel Rasmussen To: Alejandro Colomar , Peter Xu Cc: linux-man@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Axel Rasmussen X-Rspamd-Queue-Id: CC811A0036 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: um3d91eun4na1p16s5nfyj98q7hcqu15 X-HE-Tag: 1695150136-90569 X-HE-Meta: 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 bXqG9VG2 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.312132, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This process is critical for programs which depend on extra features, so it's worth mentioning here. Future commits will much more fully describe it in ioctl_userfaultfd.2. Signed-off-by: Axel Rasmussen Reviewed-by: Mike Rapoport (IBM) --- man2/userfaultfd.2 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index 40354065c..1b2af22f9 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -200,8 +200,9 @@ the application must enable it using the .B UFFDIO_API .BR ioctl (2) operation. -This operation allows a handshake between the kernel and user space -to determine the API version and supported features. +This operation allows a two-step handshake between the kernel and user space +to determine what API version and features the kernel supports, +and then to enable those features user space wants. This operation must be performed before any of the other .BR ioctl (2) operations described below (or those operations fail with the