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=-0.5 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 CA3AFC433DB for ; Sat, 2 Jan 2021 12:39:43 +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 27CE620857 for ; Sat, 2 Jan 2021 12:39:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 27CE620857 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.94) (envelope-from ) id 1kvgBn-0002gv-Hu; Sat, 02 Jan 2021 07:39:23 -0500 Received: from mail-yb1-xb2a.google.com ([2607:f8b0:4864:20::b2a]) by shelob.surriel.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kvgBk-0002f6-02 for Kernelnewbies@kernelnewbies.org; Sat, 02 Jan 2021 07:39:20 -0500 Received: by mail-yb1-xb2a.google.com with SMTP id r63so14663911ybf.5 for ; Sat, 02 Jan 2021 04:39:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to; bh=17qZyN8hYlBu1yU03pPMSg4SI41VRzUIJ+8HdWQfQro=; b=Jl0U0hoO7yGCVutIo/NlCjXDSLsFE+Z2snEoT2FySgFZ+qhAFa6stBKv2Ky+6a5Pm9 g45XdhKK4lqpAE+IqYCn9hDiMgEtWJjXDYROWn5rWbuO0Uvc0lEgTx4zoCUwwNQJ6GSc ajP5WQ7mKfFzuiSHfiCAGvXgY4TjQMagmmYv0jFXBWuZr45JAqsInRmaGlw9dGfiYRYy /45soOXBXEOU7Q2MmwnjeAxVPfi/JlHIpK40eW5Tq7HWcr7LQEKjZ0SVBkO3ZVibaSMB p2kOJPJX79qpBX2W43GCs2KNgebKQYFMiaaUBEuQXUhfr6eWGWzi5LTY1su0lAhxQDy0 7Qlw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=17qZyN8hYlBu1yU03pPMSg4SI41VRzUIJ+8HdWQfQro=; b=mSjPq5yptX8jh0wEEeJtoty8ZuXHwXBV7+EEkATip61HzfUiv61iD3K8G8hm+RejH1 4zjWX1xPY+k2EKsTRaXmeue5OasVwkI+Xs/jfsN6DVt2/WY4O9jTaaJ4Su0WYjJR/dru 2bXBDNJXtxY9O03OW25U9Te08ogFMJ5Z6ybZxdLNSBOyu7vceIdkhI8PiX8IawdzfJGY jlTa+vy00uiYnpMs93HeB0pZ9kL0toTcc6xGlvRhbaoU3FxyTNkZYFk/a6oECSkV7myC QSaj0iLgP8mHaHlRDyMsf20/vC8xuLtJNnC0Ubv5lwqTAZYz18TPQV8su+ZdWuGcBcLw BT9Q== X-Gm-Message-State: AOAM531qKgA7mi93LiEP7gARpyjCDUHaA3ErOo67PpfdPJpbXECTy/FN o7fFDzMWaKCIJ55fmo+98KekT/STNoRT514Xhh4DelCQ X-Google-Smtp-Source: ABdhPJygslvWD5A5739KpBw7HHvHm8IPEC+lVbkJvDUNZbHzTE+s0K7d8hSEw1hMoSKaKAnrnW4el7ggL4ULR0Z5GZE= X-Received: by 2002:a25:ab30:: with SMTP id u45mr92797894ybi.516.1609591158557; Sat, 02 Jan 2021 04:39:18 -0800 (PST) MIME-Version: 1.0 From: Sadanand Warrier Date: Sat, 2 Jan 2021 07:39:08 -0500 Message-ID: Subject: get_user_pages and pinning To: Kernelnewbies@kernelnewbies.org 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 Folks Since Linux uses lazy evaluation with respect to allocating memory what happens if a user process allocates memory using malloc in excess of say 8 or nine pages and calls a device ioctl and passes the user space pointer to it to be used to pin pages using get_user_pages(). This buffer is to be used for a dma read from a device. What happens if the memory isn't actually allocated (no initialization with memset or calloc etc. and all PTEs are pointing to some zero filled page) and there is no IOMMU? Thanks S _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies