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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 50840C43381 for ; Wed, 20 Mar 2019 13:43:28 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BEB422184D for ; Wed, 20 Mar 2019 13:43:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=yandex.com header.i=@yandex.com header.b="NwPtgIxK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BEB422184D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yandex.com Authentication-Results: mail.kernel.org; spf=fail smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.91) (envelope-from ) id 1h6bUd-00070z-FO; Wed, 20 Mar 2019 09:42:55 -0400 Received: from forward100p.mail.yandex.net ([77.88.28.100]) by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1h6bUb-00070r-Ab for kernelnewbies@kernelnewbies.org; Wed, 20 Mar 2019 09:42:53 -0400 Received: from mxback14g.mail.yandex.net (mxback14g.mail.yandex.net [IPv6:2a02:6b8:0:1472:2741:0:8b7:93]) by forward100p.mail.yandex.net (Yandex) with ESMTP id 78EA1598002B; Wed, 20 Mar 2019 16:42:40 +0300 (MSK) Received: from localhost (localhost [::1]) by mxback14g.mail.yandex.net (nwsmtp/Yandex) with ESMTP id zE7mF5q3XB-gdSC78ii; Wed, 20 Mar 2019 16:42:39 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.com; s=mail; t=1553089359; bh=O+gzflivqbbu/1GWGqkI9I2VSXjRT6evwud5pNh8Lds=; h=Message-Id:Date:Subject:To:From; b=NwPtgIxKScSIylJRGFVl/w3ebh7UPvjwUTPX9mwFARp1Fve05zjkaERG+nunjEDe4 PxzsnhJRFiPAl2GuH+clommIX2FO9uWoBw0AB6wqr5zwU8dP4XVvGwp62NSUxAERs8 CEpAerE+b+V+1buoSJcmRsnhAoZ6lEK2uPNqj5Cc= Authentication-Results: mxback14g.mail.yandex.net; dkim=pass header.i=@yandex.com Received: by myt2-66bcb87429e6.qloud-c.yandex.net with HTTP; Wed, 20 Mar 2019 16:42:39 +0300 From: Lev Olshvang To: kernelnewbies , linux-il Subject: What will happen if 2 processes map same physical page MIME-Version: 1.0 X-Mailer: Yamail [ http://yandex.ru ] 5.0 Date: Wed, 20 Mar 2019 16:42:39 +0300 Message-Id: <6967041553089359@myt2-66bcb87429e6.qloud-c.yandex.net> X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kernelnewbies-bounces@kernelnewbies.org Hi all, The question is it ipossiblle in Linux/MMU/TLB that 2 processes map to the same physical address? Will CPU or TLB discover that second process tries to reach occupied physical page? What if first process set page permission to read and second whats to write to this page ? Perhaps during context switch all page access permissions of first process is flashed out from MMU ? I confess I do not know what exactly happens in TLB and between Linux and hardware view of pages. I am particularly intereste in ARMv7, perhaps its architecture have some solutions to these question. Regards, Lev _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies