From nobody Sat Feb 14 02:07:15 2026 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 0A4D0CE79A9 for ; Tue, 19 Sep 2023 19:02:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232646AbjISTC0 (ORCPT ); Tue, 19 Sep 2023 15:02:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232503AbjISTCW (ORCPT ); Tue, 19 Sep 2023 15:02:22 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7298E1 for ; Tue, 19 Sep 2023 12:02:16 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-59bdac026f7so73205247b3.0 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=dRh4U7RAuuBxjfZVEwKn8TkULqOs1WF8Tqim8fb5SYDBaHHq7x8d4NSwiS5dPUSKf1 /40I5TJVFfeZudOpxciQ2lHsBf0vMKgDssIwioF2pVZTWGN+gu+wJcVAgsm3nUl0raE1 uB38eX8DxQkzksLEH4qpxi0Y4OmVDuIRh99Kx6E3MR9ep9fE0266zmxLPdNDqdwK7I0r hDRXDCldlkxBY1EWbEOSQsPYSD/ZZHoX1xwGXw/zI2QBMhA9ZoPlOS4inMXRaUDR46JT Aqr5MH2TGz0GdvC0orBkVRQSdRPr7p+lZcLbiWhAuxaN+325mPpxHJMJ8I5ektnJHEtl Ygyg== X-Gm-Message-State: AOJu0YycEw3Qy03Q8xo5Biljt1dYYt7UBRJbiZU3obbPG5u06X1mo9s5 KNZ8aX/9Zx3fcbdAI1+vkkP79a2dB/ya+HfHAFiH 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 spa= ce +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 --=20 2.42.0.459.ge4e396fd5e-goog