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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 80F60C4332D for ; Wed, 10 Mar 2021 22:24:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66FF364FC6 for ; Wed, 10 Mar 2021 22:24:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233199AbhCJWXj (ORCPT ); Wed, 10 Mar 2021 17:23:39 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:38846 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231368AbhCJWXH (ORCPT ); Wed, 10 Mar 2021 17:23:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615414986; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xTi7eK4FhauapOMog+x2j3yLdISM1j6yYqbUEE/lj8k=; b=EOny+7YwKvV3oGXe6aBsGnOP4vzQGK7BnY7M6M295Md192TZZ9eYjIZaKFYQNkXkomNBxL rVr3lq9HAPFPgSPASEUIfLsQA5ABmWS1YvoYQVAx9cD+COC75bhfaMHmrnvgWdRcWWrf0J RU0pC0KZ6sda1jX6lYbFbb8fePODhEk= Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-523-EX8JKWZuP_e-MyNOnt2_vA-1; Wed, 10 Mar 2021 17:23:04 -0500 X-MC-Unique: EX8JKWZuP_e-MyNOnt2_vA-1 Received: by mail-qk1-f198.google.com with SMTP id y9so13927289qki.14 for ; Wed, 10 Mar 2021 14:23:04 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=xTi7eK4FhauapOMog+x2j3yLdISM1j6yYqbUEE/lj8k=; b=BjQcxHvds3eZNqGCRE9t7eEaBUaiFr8dcrqB/s2m98vqeHdckHfaC2+4EcUdFETW6O 1sx2VUrG+gMOYcSs2yotE/6Hjs/lN90ysPjtVXSQD3ULpMRKUfEx9ztj3zjOuB0SSWhu 2y3vlJIybhEkFnZHW5DBQrujZDaGM0nqvxjdOHS7Z7ZYStRC/uFLA58i2WWNNfwgrE/M ils+gSU9jvpmUxjAZsHZYHgbFdvP1kE3kcIaR7mSsqEVY8bjr7hH7G/2axLwmK8UYmmk +Rm25HfxJlqNL+/4JiwaG3sjVKKqPfoW1uWPj51Op2cQOkqW8g5qh5eKAxtkKK8aJyIZ xuPg== X-Gm-Message-State: AOAM530RbGsXPGWp0ng4oW1CX57nB8aUMduCJ7WZ8E8i0T5JLS5RLDIf TefRRFGwc9FdiuTbsql2BRMink915y+dWXTnyNoXTE/Mgm2BFDaLVwo01fLSoSIWHPCRqxMXkCl hCbUQvhzONTkN/smNEJH0MhkC X-Received: by 2002:a37:b801:: with SMTP id i1mr4941131qkf.133.1615414983456; Wed, 10 Mar 2021 14:23:03 -0800 (PST) X-Google-Smtp-Source: ABdhPJwU243DD5kOgxdOCxo20TQ0iqAimdDflbdLiodAf/V734MqCBcbaDiFEuQUCmE8qO5s1PRH9Q== X-Received: by 2002:a37:b801:: with SMTP id i1mr4941116qkf.133.1615414983236; Wed, 10 Mar 2021 14:23:03 -0800 (PST) Received: from xz-x1.redhat.com ([142.126.89.138]) by smtp.gmail.com with ESMTPSA id e18sm451364qtr.52.2021.03.10.14.23.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Mar 2021 14:23:02 -0800 (PST) From: Peter Xu To: linux-man@vger.kernel.org Cc: Andrea Arcangeli , Michael Kerrisk , Axel Rasmussen , linux-kernel@vger.kernel.org, peterx@redhat.com, Linux MM Mailing List , Andrew Morton , Alejandro Colomar , Nadav Amit , Mike Rapoport Subject: [PATCH v3 1/4] userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Date: Wed, 10 Mar 2021 17:22:57 -0500 Message-Id: <20210310222300.200054-2-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210310222300.200054-1-peterx@redhat.com> References: <20210310222300.200054-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org UFFD_FEATURE_THREAD_ID is supported since Linux 4.14. Signed-off-by: Peter Xu --- man2/userfaultfd.2 | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index e7dc9f813..555e37409 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -77,6 +77,13 @@ When the last file descriptor referring to a userfaultfd object is closed, all memory ranges that were registered with the object are unregistered and unread events are flushed. .\" +.PP +Since Linux 4.14, userfaultfd page fault message can selectively embed faulting +thread ID information into the fault message. +One needs to enable this feature explicitly using the +.BR UFFD_FEATURE_THREAD_ID +feature bit when initializing the userfaultfd context. +By default, thread ID reporting is diabled. .SS Usage The userfaultfd mechanism is designed to allow a thread in a multithreaded program to perform user-space paging for the other threads in the process. @@ -229,6 +236,9 @@ struct uffd_msg { struct { __u64 flags; /* Flags describing fault */ __u64 address; /* Faulting address */ + union { + __u32 ptid; /* Thread ID of the fault */ + } feat; } pagefault; struct { /* Since Linux 4.11 */ @@ -358,6 +368,9 @@ otherwise it is a read fault. .\" UFFD_PAGEFAULT_FLAG_WP is not yet supported. .RE .TP +.I pagefault.feat.pid +The thread ID that triggered the page fault. +.TP .I fork.ufd The file descriptor associated with the userfault object created for the child created by -- 2.26.2