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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0B5BCE79A9 for ; Tue, 19 Sep 2023 19:02:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232524AbjISTCX (ORCPT ); Tue, 19 Sep 2023 15:02:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232490AbjISTCW (ORCPT ); Tue, 19 Sep 2023 15:02:22 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5D66B3 for ; Tue, 19 Sep 2023 12:02:16 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-597f461adc5so73017597b3.1 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=vger.kernel.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=TL7YK71y+TUTy6fGHYiqdt4EtznmZCsTiHX38kHatN4xhHv67/jiXlPuGF2TixAK/m AwAnc1huXwj7Kkc1XDnMP1lT4t+s/lZd7VTuW6gu2fgOFm1OiPF7V4JZgnOuavWSO+EB OylC/CtOFWRfzrNpB0UKREr5Bd6tSYckKJXohuyIjLLv3vUrmi3dlHv4IahrJ2oaB3em UOpkZCFgCRhIanNHMSCO4awRhDvx3N9Y2pVAjUXrKBO6aqF93RDswWshoCVSVLu3ZgF2 km9BZHT3khi3N+Oi4nroprbc4fCKPDIMV1dfsdu29GaMjWZnK1xf66H5lDijGxxOdSrO h/lA== 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=mpQf8qYr2bf5I1ce8GWaeYvG2GHunCWxRj8yp3OETkVfzWw8g5C1PUMNmjXxWoEbPp p3RUkaCcwMjpQfhuEw5RlUNImdY82hQzc8TWI8LxGX8xV+kAqtpfKWf5hlmXI/7FGMa2 5NexzE3ZvthdV1OO0KI702K9hD43LAZA3dFDhvJN+bAYxLVY1XRx2YZbNf9AbTYRq/0E W6wKetbf9vzcQpHZgTMnec56W6bdsT9dbscu/a0y7OVqubYJJPEIiQLFRzriilOp80cs RwCiOwRdwnxHHo/nyohG6/2jbeIWcgmNxoiTiuTJyBgj9tCFQ3Ncs44Vnuc/+T83EWOE hUuw== X-Gm-Message-State: AOJu0YzglV6p94Noq/07vsJxksTPNhNdYRv3KIgLSvOlyy7b/mJes/H3 cJcuetfaDvOjGNPjk4KENxn0O8MCOKN9aTpcspLT 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org 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 --- 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 -- 2.42.0.459.ge4e396fd5e-goog