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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 BC10DC83006 for ; Thu, 30 Apr 2020 08:20:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88EF52073E for ; Thu, 30 Apr 2020 08:20:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="CNsohpya" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726543AbgD3IUh (ORCPT ); Thu, 30 Apr 2020 04:20:37 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:58322 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726621AbgD3IUg (ORCPT ); Thu, 30 Apr 2020 04:20:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588234834; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Oj3Gb/CDuSGT8ulKk/yMbVBXnCO14VNDywwKRzXNY0s=; b=CNsohpyauJPtjQ/VmSkfpGVmgmJU9KEMOK6sD+Xe+GCdvedOQwALCwy3HRRUPAyXJbSBR/ 1r3aGP4tkGvfblDR2fQBiXzEbCJ6fxVXxdkKM346i2r71bEEfd/EGUFxRwQpLpTBlefNaX +d5s6L3UUyHnZ1sigepsUvdzooTywIk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-286-dm43KJQWPbG-0H4SvcZs2g-1; Thu, 30 Apr 2020 04:20:32 -0400 X-MC-Unique: dm43KJQWPbG-0H4SvcZs2g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 848AB1902EA2; Thu, 30 Apr 2020 08:20:29 +0000 (UTC) Received: from [10.36.113.172] (ovpn-113-172.ams2.redhat.com [10.36.113.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 44A771002395; Thu, 30 Apr 2020 08:20:22 +0000 (UTC) Subject: Re: [PATCH v1 2/3] mm/memory_hotplug: Introduce MHP_DRIVER_MANAGED To: Dan Williams Cc: Linux Kernel Mailing List , Linux MM , virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, linuxppc-dev , Linux ACPI , linux-nvdimm , linux-hyperv@vger.kernel.org, linux-s390 , xen-devel , Michal Hocko , Andrew Morton , "Michael S . Tsirkin" , Michal Hocko , Pankaj Gupta , Wei Yang , Baoquan He , Eric Biederman , Pavel Tatashin , Dave Hansen References: <20200429160803.109056-1-david@redhat.com> <20200429160803.109056-3-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Thu, 30 Apr 2020 10:20:21 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Content-Transfer-Encoding: quoted-printable Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On 30.04.20 10:11, Dan Williams wrote: > On Thu, Apr 30, 2020 at 12:20 AM David Hildenbrand w= rote: >> >> On 29.04.20 18:08, David Hildenbrand wrote: >>> Some paravirtualized devices that add memory via add_memory() and >>> friends (esp. virtio-mem) don't want to create entries in >>> /sys/firmware/memmap/ - primarily to hinder kexec from adding this >>> memory to the boot memmap of the kexec kernel. >>> >>> In fact, such memory is never exposed via the firmware (e.g., e820), = but >>> only via the device, so exposing this memory via /sys/firmware/memmap= / is >>> wrong: >>> "kexec needs the raw firmware-provided memory map to setup the >>> parameter segment of the kernel that should be booted with >>> kexec. Also, the raw memory map is useful for debugging. For >>> that reason, /sys/firmware/memmap is an interface that provides >>> the raw memory map to userspace." [1] >>> >>> We want to let user space know that memory which is always detected, >>> added, and managed via a (device) driver - like memory managed by >>> virtio-mem - is special. It cannot be used for placing kexec segments >>> and the (device) driver is responsible for re-adding memory that >>> (eventually shrunk/grown/defragmented) memory after a reboot/kexec. I= t >>> should e.g., not be added to a fixed up firmware memmap. However, it = should >>> be dumped by kdump. >>> >>> Also, such memory could behave differently than an ordinary DIMM - e.= g., >>> memory managed by virtio-mem can have holes inside added memory resou= rce, >>> which should not be touched, especially for writing. >>> >>> Let's expose that memory as "System RAM (driver managed)" e.g., via >>> /pro/iomem. >>> >>> We don't have to worry about firmware_map_remove() on the removal pat= h. >>> If there is no entry, it will simply return with -EINVAL. >>> >>> [1] https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-firmwa= re-memmap >>> >>> Cc: Andrew Morton >>> Cc: Michal Hocko >>> Cc: Pankaj Gupta >>> Cc: Wei Yang >>> Cc: Baoquan He >>> Cc: Eric Biederman >>> Signed-off-by: David Hildenbrand >>> --- >>> include/linux/memory_hotplug.h | 8 ++++++++ >>> mm/memory_hotplug.c | 20 ++++++++++++++++---- >>> 2 files changed, 24 insertions(+), 4 deletions(-) >>> >>> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_ho= tplug.h >>> index bf0e3edb8688..cc538584b39e 100644 >>> --- a/include/linux/memory_hotplug.h >>> +++ b/include/linux/memory_hotplug.h >>> @@ -68,6 +68,14 @@ struct mhp_params { >>> pgprot_t pgprot; >>> }; >>> >>> +/* Flags used for add_memory() and friends. */ >>> + >>> +/* >>> + * Don't create entries in /sys/firmware/memmap/ and expose memory a= s >>> + * "System RAM (driver managed)" in e.g., /proc/iomem >>> + */ >>> +#define MHP_DRIVER_MANAGED 1 >>> + >>> /* >>> * Zone resizing functions >>> * >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index ebdf6541d074..cfa0721280aa 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -98,11 +98,11 @@ void mem_hotplug_done(void) >>> u64 max_mem_size =3D U64_MAX; >>> >>> /* add this memory to iomem resource */ >>> -static struct resource *register_memory_resource(u64 start, u64 size= ) >>> +static struct resource *register_memory_resource(u64 start, u64 size= , >>> + const char *resource_n= ame) >>> { >>> struct resource *res; >>> unsigned long flags =3D IORESOURCE_SYSTEM_RAM | IORESOURCE_BUS= Y; >>> - char *resource_name =3D "System RAM"; >>> >>> /* >>> * Make sure value parsed from 'mem=3D' only restricts memory a= dding >>> @@ -1058,7 +1058,8 @@ int __ref add_memory_resource(int nid, struct r= esource *res, >>> BUG_ON(ret); >>> >>> /* create new memmap entry */ >>> - firmware_map_add_hotplug(start, start + size, "System RAM"); >>> + if (!(flags & MHP_DRIVER_MANAGED)) >>> + firmware_map_add_hotplug(start, start + size, "System R= AM"); >>> >>> /* device_online() will take the lock when calling online_pages= () */ >>> mem_hotplug_done(); >>> @@ -1081,10 +1082,21 @@ int __ref add_memory_resource(int nid, struct= resource *res, >>> /* requires device_hotplug_lock, see add_memory_resource() */ >>> int __ref __add_memory(int nid, u64 start, u64 size, unsigned long f= lags) >>> { >>> + const char *resource_name =3D "System RAM"; >>> struct resource *res; >>> int ret; >>> >>> - res =3D register_memory_resource(start, size); >>> + /* >>> + * Indicate that memory managed by a driver is special. It's al= ways >>> + * detected and added via a driver, should not be given to the = kexec >>> + * kernel for booting when manually crafting the firmware memma= p, and >>> + * no kexec segments should be placed on it. However, kdump sho= uld >>> + * dump this memory. >>> + */ >>> + if (flags & MHP_DRIVER_MANAGED) >>> + resource_name =3D "System RAM (driver managed)"; >>> + >>> + res =3D register_memory_resource(start, size, resource_name); >>> if (IS_ERR(res)) >>> return PTR_ERR(res); >>> >>> >> >> BTW, I was wondering if this is actually also something that >> drivers/dax/kmem.c wants to use for adding memory. >> >> Just because we decided to use some DAX memory in the current kernel a= s >> system ram, doesn't mean we should make that decision for the kexec >> kernel (e.g., using it as initial memory, placing kexec binaries onto >> it, etc.). This is also not what we would observe during a real reboot= . >=20 > Agree. >=20 >> I can see that the "System RAM" resource will show up as child resourc= e >> under the device e.g., in /proc/iomem. >> >> However, entries in /sys/firmware/memmap/ are created as "System RAM". >=20 > True. Do you think this rename should just be limited to what type > /sys/firmware/memmap/ emits? I have the concern, but no proof We could split this patch into MHP_NO_FIRMWARE_MEMMAP (create firmware memmap entries) and MHP_DRIVER_MANAGED (name of the resource) See below, the latter might not be needed. > currently, that there are /proc/iomem walkers that explicitly look for > "System RAM", but might be thrown off by "System RAM (driver > managed)". I was not aware of /sys/firmware/memmap until about 5 > minutes ago. The only two users of /proc/iomem I am aware of are kexec-tools and some s390x tools. kexec-tools on x86-64 uses /sys/firmware/memmap to craft the initial memmap, but uses /proc/iomem to a) Find places for kexec images b) Detect memory regions to dump via kdump I am not yet sure if we really need the "System RAM (driver managed)" part. If we can teach kexec-tools to a) Don't place kexec images on "System RAM" that has a parent resource (most likely requires kexec-tools changes) b) Consider for kdump "System RAM" that has a parent resource we might be able to avoid renaming that. (I assume that's already done) E.g., regarding virtio-mem (patch #3) I am currently also looking into creating a parent resource instead, like dax/kmem to avoid the rename: :/# cat /proc/iomem 00000000-00000fff : Reserved [...] 100000000-13fffffff : System RAM 140000000-33fffffff : virtio0 140000000-147ffffff : System RAM 148000000-14fffffff : System RAM 150000000-157ffffff : System RAM 340000000-303fffffff : virtio1 340000000-347ffffff : System RAM 3280000000-32ffffffff : PCI Bus 0000:00 --=20 Thanks, David / dhildenb