From patchwork Thu Jul 6 22:50:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 699933 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 ACC02C001DD for ; Thu, 6 Jul 2023 22:51:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231693AbjGFWv1 (ORCPT ); Thu, 6 Jul 2023 18:51:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231450AbjGFWvQ (ORCPT ); Thu, 6 Jul 2023 18:51:16 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62E221FF7 for ; Thu, 6 Jul 2023 15:51:03 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-564fb1018bcso13233937b3.0 for ; Thu, 06 Jul 2023 15:51:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688683862; x=1691275862; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=7OMVl3YxFVN2A+Ry/UxbO1YmCHHRZcxw7VDxaJg9ek4=; b=MUCpPcJ5Cgcqj6eW6sHdBBG776f5QGOT4kgvGYw/zAIra7r+ur1/6MP7Dq6MkoSZmq 4xRE3PYyIXD4h8qZWQWCXhWmcWP1AwGUjGAf2ElqV4yAkcG0gjhOddOoakQQadmYz+QD Is/7A9d1hSTithrMC6POOEAOeFEch61LmagZDJM30S0vYIcKNDDe5/OQ3z3oRxh6zHQl utpA3lGtPFljt8j9Ntkp9LhkEyWfCZ3raeDW8NKQTH9gVvZpq5Wizvy5vkyeCh1Pwwja CGEW2G1lqZ2p9p/Ga+J136aVMeRPFS8hQNLl5QI5DDjAJCWHkUOphl3NTJbnSXMCQUoE o8sw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688683862; x=1691275862; 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=7OMVl3YxFVN2A+Ry/UxbO1YmCHHRZcxw7VDxaJg9ek4=; b=RUcXj+oM3JM1MeLUAmNoRVuvjqXmEDx5o5NwbrJKCfTAncsHz8qt08/U6hdKFl6Bji A1m9Ewn8rl0wVPHgJjfjnqsJgCbTc+UPpoA6asFsbILV2YzsssYXJYhQuQPnML6IVA3N cX7kWQziYu8c7DHI6bzt+vOa7mAQBzdjbL5dqdKqE4+NxfBmA3wm9veWtU4xQWSI+Qo9 XWvw3eKlPVsTsDvkAX/pFJxX9Y0Jct/lRKUx1HR3qn+5XGQ+Ej3UZ2L5KNKFW/tE1Dma IIDKCSwdJpAmCa4hp+iPcBqslAImBFlyZy7auSPF7H5Mpjhf6Fl2KPDXVGOZEhWcyyDs p3OA== X-Gm-Message-State: ABy/qLa3vZyodNWPQ6/pOORkUmv7ohWb61VaZWYOzH9X7mHl9oIEspoK 5rgHmWM9HO7dxBYNP1UhG5gKQcPAt394iUPSIQoO X-Google-Smtp-Source: APBJJlG1dkyvwdYp0IICzgcbHzfcY4HpHckyy/miTsDbBSll9Umrn8xTYfU/5fbclpora7Bohc9XblNeG3IvM415E6Ta X-Received: from axel.svl.corp.google.com ([2620:15c:2a3:200:bec3:2b1c:87a:fca2]) (user=axelrasmussen job=sendgmr) by 2002:a81:af07:0:b0:565:a33a:a49f with SMTP id n7-20020a81af07000000b00565a33aa49fmr25333ywh.6.1688683862421; Thu, 06 Jul 2023 15:51:02 -0700 (PDT) Date: Thu, 6 Jul 2023 15:50:34 -0700 In-Reply-To: <20230706225037.1164380-1-axelrasmussen@google.com> Mime-Version: 1.0 References: <20230706225037.1164380-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.41.0.255.g8b1d071c50-goog Message-ID: <20230706225037.1164380-7-axelrasmussen@google.com> Subject: [PATCH v3 6/8] mm: userfaultfd: document and enable new UFFDIO_POISON feature From: Axel Rasmussen To: Alexander Viro , Andrew Morton , Brian Geffon , Christian Brauner , David Hildenbrand , Gaosheng Cui , Huang Ying , Hugh Dickins , James Houghton , "Jan Alexander Steffens (heftig)" , Jiaqi Yan , Jonathan Corbet , Kefeng Wang , "Liam R. Howlett" , Miaohe Lin , Mike Kravetz , "Mike Rapoport (IBM)" , Muchun Song , Nadav Amit , Naoya Horiguchi , Peter Xu , Ryan Roberts , Shuah Khan , Suleiman Souhlal , Suren Baghdasaryan , "T.J. Alumbaugh" , Yu Zhao , ZhangPeng Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Axel Rasmussen Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Update the userfaultfd API to advertise this feature as part of feature flags and supported ioctls (returned upon registration). Add basic documentation describing the new feature. Acked-by: Peter Xu Signed-off-by: Axel Rasmussen --- Documentation/admin-guide/mm/userfaultfd.rst | 15 +++++++++++++++ include/uapi/linux/userfaultfd.h | 9 ++++++--- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 7c304e432205..4349a8c2b978 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -244,6 +244,21 @@ write-protected (so future writes will also result in a WP fault). These ioctls support a mode flag (``UFFDIO_COPY_MODE_WP`` or ``UFFDIO_CONTINUE_MODE_WP`` respectively) to configure the mapping this way. +Memory Poisioning Emulation +--------------------------- + +In response to a fault (either missing or minor), an action userspace can +take to "resolve" it is to issue a ``UFFDIO_POISON``. This will cause any +future faulters to either get a SIGBUS, or in KVM's case the guest will +receive an MCE as if there were hardware memory poisoning. + +This is used to emulate hardware memory poisoning. Imagine a VM running on a +machine which experiences a real hardware memory error. Later, we live migrate +the VM to another physical machine. Since we want the migration to be +transparent to the guest, we want that same address range to act as if it was +still poisoned, even though it's on a new physical host which ostensibly +doesn't have a memory error in the exact same spot. + QEMU/KVM ======== diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index b5f07eacc697..62151706c5a3 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -39,7 +39,8 @@ UFFD_FEATURE_MINOR_SHMEM | \ UFFD_FEATURE_EXACT_ADDRESS | \ UFFD_FEATURE_WP_HUGETLBFS_SHMEM | \ - UFFD_FEATURE_WP_UNPOPULATED) + UFFD_FEATURE_WP_UNPOPULATED | \ + UFFD_FEATURE_POISON) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -49,12 +50,14 @@ (__u64)1 << _UFFDIO_COPY | \ (__u64)1 << _UFFDIO_ZEROPAGE | \ (__u64)1 << _UFFDIO_WRITEPROTECT | \ - (__u64)1 << _UFFDIO_CONTINUE) + (__u64)1 << _UFFDIO_CONTINUE | \ + (__u64)1 << _UFFDIO_POISON) #define UFFD_API_RANGE_IOCTLS_BASIC \ ((__u64)1 << _UFFDIO_WAKE | \ (__u64)1 << _UFFDIO_COPY | \ + (__u64)1 << _UFFDIO_WRITEPROTECT | \ (__u64)1 << _UFFDIO_CONTINUE | \ - (__u64)1 << _UFFDIO_WRITEPROTECT) + (__u64)1 << _UFFDIO_POISON) /* * Valid ioctl command number range with this API is from 0x00 to