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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CEF9C433EF for ; Tue, 26 Apr 2022 21:34:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 886506B0074; Tue, 26 Apr 2022 17:34:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 835686B0075; Tue, 26 Apr 2022 17:34:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 723ED6B0078; Tue, 26 Apr 2022 17:34:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 629066B0074 for ; Tue, 26 Apr 2022 17:34:05 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 379C0261BD for ; Tue, 26 Apr 2022 21:34:05 +0000 (UTC) X-FDA: 79400333250.14.6C3A32F Received: from mail-io1-f47.google.com (mail-io1-f47.google.com [209.85.166.47]) by imf26.hostedemail.com (Postfix) with ESMTP id 0AF4F140047 for ; Tue, 26 Apr 2022 21:34:02 +0000 (UTC) Received: by mail-io1-f47.google.com with SMTP id r28so289092iot.1 for ; Tue, 26 Apr 2022 14:34:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zJHneikLXEGfJde4krQasd9PQhsFRpApoS4ZRag7+RU=; b=EdwxR0V/0R58E5VQDj0HrytGDcfRa0ZaI7Me6rDBjirAgNHRbWWWvGaw7HmQEIGzu+ 8UTTpBJpVmtohKiGL5cVYIq8PicWJvFUQVly2vSP4TS+56W86k/aX6l5WCrdoFzyILM+ 1Yehf40AqvUszrZodWCBswvT50v8vrsYb0CT9VT0ik1assb3s50rjI/Ghc6ERMC0+hQS kngQQpUrenrx0Z/CG7kuYI7vOHHB9pxCvklytawOfmTdu9cTLRddizluzNirEjBtvgHq /7wjZvrPSoiAuTCiyBqcBwBGz7SjzYicglmkQ0p2ZcHJZmj17y1/IkCZAoejAg68UMHJ xOsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zJHneikLXEGfJde4krQasd9PQhsFRpApoS4ZRag7+RU=; b=VudXmxC3RucRLhEHvHqhMZVDubHUMrVnTf8kYKARnJdZLZAdTnMV2iqtKFUXNQeFnd 4ZTXspWqKYNgc8HYQn683vtXgXAt4ZKTk1wezaIZdqoM+h29LHz1g+9S0HDuUaNuuqr9 RmgNqQjAYI9cxeidiB0eMiu4Vj6qe8y3Yg1g/CsGmWUXHGDskIFzYyxObO4eplxHOsVa Rw80kGdOjBwwzJQrMoBW7poWAF4uZ9QSBaakcJYXxCsKX/22wqBGv6yFh0wYiM8bSlc/ ihQzgnXwwL6qLyiSxkgnFw087QDpolrNIPmPSfN5LxDQULEEheQE1NYjGb8+1B41fCSp exEQ== X-Gm-Message-State: AOAM532cXWlCih3kUh2j+lUpS4J/g+t0eVpLzE2yIepJ0SCh6ZKupH7V tlgKQvwg2G2UIw84ANfIl83zIBFiE6mW5B4fwJXxJA== X-Google-Smtp-Source: ABdhPJyGNR5sOXzGqUeKg6keEazd9H9Z8L/jAzBgMCoHI+lyyK7gNjS+2erCu0X4dzgJTpnr7YSLg3mNpJ5fsfcJHI0= X-Received: by 2002:a5d:9448:0:b0:657:24e0:c0b2 with SMTP id x8-20020a5d9448000000b0065724e0c0b2mr10388348ior.167.1651008843696; Tue, 26 Apr 2022 14:34:03 -0700 (PDT) MIME-Version: 1.0 References: <20220422212945.2227722-1-axelrasmussen@google.com> <20220422212945.2227722-3-axelrasmussen@google.com> In-Reply-To: From: Axel Rasmussen Date: Tue, 26 Apr 2022 14:33:27 -0700 Message-ID: Subject: Re: [PATCH v2 2/6] userfaultfd: add /dev/userfaultfd for fine grained access control To: Peter Xu Cc: Alexander Viro , Andrew Morton , Charan Teja Reddy , Dave Hansen , "Dmitry V . Levin" , Gleb Fotengauer-Malinovskiy , Hugh Dickins , Jan Kara , Jonathan Corbet , Mel Gorman , Mike Kravetz , Mike Rapoport , Nadav Amit , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , zhangyi , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, LKML , Linux MM , Linuxkselftest Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="EdwxR0V/"; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf26.hostedemail.com: domain of axelrasmussen@google.com designates 209.85.166.47 as permitted sender) smtp.mailfrom=axelrasmussen@google.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 0AF4F140047 X-Rspam-User: X-Stat-Signature: z6qmhtefwsrc758ntbypeuudy6oezbnq X-HE-Tag: 1651008842-299549 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 26, 2022 at 1:33 PM Peter Xu wrote: > > Axel, > > On Fri, Apr 22, 2022 at 02:29:41PM -0700, Axel Rasmussen wrote: > > @@ -65,6 +66,8 @@ struct userfaultfd_ctx { > > unsigned int flags; > > /* features requested from the userspace */ > > unsigned int features; > > + /* whether or not to handle kernel faults */ > > + bool handle_kernel_faults; > > Could you help explain why we need this bool? I failed to figure out > myself on the difference against "!(ctx->flags & UFFD_USER_MODE_ONLY)". Ah, yeah you're right, we can get rid of it and just rely on UFFD_USER_MODE_ONLY. Just to add context, in a previous version I never sent out, I had: ctx->handle_kernel_faults = userfaultfd_allowed(...); That's wrong for other reasons, but if we were going to do that we'd have to store the result, since it's a function not just of the flags, but also of the method used to create the userfaultfd. I changed this without also dropping the boolean, which can now be cleaned up. I'll include this change in a v3. > > Thanks, > > -- > Peter Xu >