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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 16F1ED132AA for ; Mon, 4 Nov 2024 10:39:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t7uUX-0006T7-Hy; Mon, 04 Nov 2024 05:39:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t7uUW-0006QK-7T for qemu-devel@nongnu.org; Mon, 04 Nov 2024 05:39:24 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t7uUU-0001oE-0j for qemu-devel@nongnu.org; Mon, 04 Nov 2024 05:39:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1730716759; 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=7rmIURTdO/D6oMXKI5jaWbblDiudfGMU1wCX2eYZVAc=; b=YWDINMhdJBc/NyfTy7JM6Ei2znfC6Lz7FC/d/31OqIOP/PTL59aP7glvr59fNJx6DQf0Hq QstfezTfotEWS2PQrjL9ElukV0ZRDiQlsqgNKj4ch0LPGT5Px9Di0iWjtAxhNgABNyqE0t nM0JYbsH2s/5ls+re1oVMe7rID4iB4g= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-197-H6j5EH12OCiTVqAtulp62w-1; Mon, 04 Nov 2024 05:39:18 -0500 X-MC-Unique: H6j5EH12OCiTVqAtulp62w-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-37d45de8bbfso2931847f8f.3 for ; Mon, 04 Nov 2024 02:39:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730716757; x=1731321557; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=7rmIURTdO/D6oMXKI5jaWbblDiudfGMU1wCX2eYZVAc=; b=frookj35hfktL5ZY8qn9B75Xj6Mdi5IBlCowDSyv8yYRQa/Zsyc6v3+bInG+/u4Ht5 0n82cp+SdDX+sL0cnv7KVKn/574N7fOhK9OeqflJU6wE46IMFs9ZG9L6eYCpafPZE9Ys HdQBwj8zMo6SEy1wiTXkLHUZ8MQlk5Zxc2aHj/AzaIgh5YyLiPUK8TNnTYe9pXE4PKf5 mgi5jaTyTy8+5Mla1pMaNHXOCVldhk8KXgRXG+f1b7DdIXwemF9Pr3DkgL/Y7SqNTTYi e9iGSmqT2KH4yqfx6AYXf3qeNyA2kGxmIlos8/6P91pmOyfi7PvxFP45IVQFR2RMNf2s EchA== X-Forwarded-Encrypted: i=1; AJvYcCV5pTjf3DqysdOFWb4dXi0tfyyW6wG0F0m2z4MtSIthGCDB7HZnVEWd4H95JLg225wFV4Rdn3eEwa/7@nongnu.org X-Gm-Message-State: AOJu0Yw9WXB4YkszW1CuNnA/O4KB2nzctw9mw+meJsIJLrbcpKfNKbo8 mE/L0XSnN9nNURmOmrL61kqnA//j6jjkANhq/Hqd7wCyYtqJdQfix17ydG5iY8crjA4AHnGD3FB 7Q0HXD27FYo/wzPMkUMQhj3JqROVyXk5dFJBWEUZatdR0hcRccuhA X-Received: by 2002:a5d:5a13:0:b0:37c:fbf8:fc4 with SMTP id ffacd0b85a97d-381c7af3be3mr13506992f8f.59.1730716757228; Mon, 04 Nov 2024 02:39:17 -0800 (PST) X-Google-Smtp-Source: AGHT+IEKTr83jraCx6epSQ9nnQhtB0KqPL6S477hNVn0L87FYC8lSBVDA1L3O3RguuZkZdTMcpFKuA== X-Received: by 2002:a5d:5a13:0:b0:37c:fbf8:fc4 with SMTP id ffacd0b85a97d-381c7af3be3mr13506954f8f.59.1730716756742; Mon, 04 Nov 2024 02:39:16 -0800 (PST) Received: from ?IPV6:2a09:80c0:192:0:5dac:bf3d:c41:c3e7? ([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-381c10e74casm12795502f8f.65.2024.11.04.02.39.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Nov 2024 02:39:16 -0800 (PST) Message-ID: <78fa25f1-03dc-400c-a604-998c53e4fbce@redhat.com> Date: Mon, 4 Nov 2024 11:39:15 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V3 01/16] machine: anon-alloc option To: Steve Sistare , qemu-devel@nongnu.org Cc: Peter Xu , Fabiano Rosas , Marcel Apfelbaum , Eduardo Habkost , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" , Markus Armbruster References: <1730468875-249970-1-git-send-email-steven.sistare@oracle.com> <1730468875-249970-2-git-send-email-steven.sistare@oracle.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <1730468875-249970-2-git-send-email-steven.sistare@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.34, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 01.11.24 14:47, Steve Sistare wrote: > Allocate anonymous memory using mmap MAP_ANON or memfd_create depending > on the value of the anon-alloc machine property. This option applies to > memory allocated as a side effect of creating various devices. It does > not apply to memory-backend-objects, whether explicitly specified on > the command line, or implicitly created by the -m command line option. > > The memfd option is intended to support new migration modes, in which the > memory region can be transferred in place to a new QEMU process, by sending > the memfd file descriptor to the process. Memory contents are preserved, > and if the mode also transfers device descriptors, then pages that are > locked in memory for DMA remain locked. This behavior is a pre-requisite > for supporting vfio, vdpa, and iommufd devices with the new modes. A more portable, non-Linux specific variant of this will be using shm, similar to backends/hostmem-shm.c. Likely we should be using that instead of memfd, or try hiding the details. See below. [...] > @@ -69,6 +70,8 @@ > > #include "qemu/pmem.h" > > +#include "qapi/qapi-types-migration.h" > +#include "migration/options.h" > #include "migration/vmstate.h" > > #include "qemu/range.h" > @@ -1849,6 +1852,35 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) > qemu_mutex_unlock_ramlist(); > return; > } > + > + } else if (current_machine->anon_alloc == ANON_ALLOC_OPTION_MEMFD && > + !object_dynamic_cast(new_block->mr->parent_obj.parent, > + TYPE_MEMORY_BACKEND)) { This looks a bit and hackish, and I don't think ram_block_add() is the right place where this should be. It should likely happen in the caller. We already do have two ways of allocating "shared anonymous memory": (1) memory-backend-ram,share=on (2) memory-backend-shm (2) gives us an fd as it uses shm_open(), (1) doesn't give us an fd as it uses MAP_ANON|MAP_SHARED. (1) is really only a corner case use case [1]. [there is also Linux specific memfd, which gives us more flexibility with hugetlb etc, but for the purpose here shm should likely be sufficient?] So why not make (1) behave like (2) and move that handling into qemu_ram_alloc_internal(), from where we can easily enable it using a new RMA_SHARED flag? So as a first step, something like: From 4b7b760c6e54cf05addca6728edc19adbec1588a Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 4 Nov 2024 11:29:22 +0100 Subject: [PATCH] tmp Signed-off-by: David Hildenbrand --- backends/hostmem-shm.c | 56 ++++---------------------------- system/physmem.c | 73 ++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 76 insertions(+), 53 deletions(-) diff --git a/backends/hostmem-shm.c b/backends/hostmem-shm.c index 374edc3db8..0f33b35e9c 100644 --- a/backends/hostmem-shm.c +++ b/backends/hostmem-shm.c @@ -25,11 +25,8 @@ struct HostMemoryBackendShm { static bool shm_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) { - g_autoptr(GString) shm_name = g_string_new(NULL); - g_autofree char *backend_name = NULL; + g_autofree char *name = NULL; uint32_t ram_flags; - int fd, oflag; - mode_t mode; if (!backend->size) { error_setg(errp, "can't create shm backend with size 0"); @@ -41,54 +38,13 @@ shm_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) return false; } - /* - * Let's use `mode = 0` because we don't want other processes to open our - * memory unless we share the file descriptor with them. - */ - mode = 0; - oflag = O_RDWR | O_CREAT | O_EXCL; - backend_name = host_memory_backend_get_name(backend); - - /* - * Some operating systems allow creating anonymous POSIX shared memory - * objects (e.g. FreeBSD provides the SHM_ANON constant), but this is not - * defined by POSIX, so let's create a unique name. - * - * From Linux's shm_open(3) man-page: - * For portable use, a shared memory object should be identified - * by a name of the form /somename;" - */ - g_string_printf(shm_name, "/qemu-" FMT_pid "-shm-%s", getpid(), - backend_name); - - fd = shm_open(shm_name->str, oflag, mode); - if (fd < 0) { - error_setg_errno(errp, errno, - "failed to create POSIX shared memory"); - return false; - } - - /* - * We have the file descriptor, so we no longer need to expose the - * POSIX shared memory object. However it will remain allocated as long as - * there are file descriptors pointing to it. - */ - shm_unlink(shm_name->str); - - if (ftruncate(fd, backend->size) == -1) { - error_setg_errno(errp, errno, - "failed to resize POSIX shared memory to %" PRIu64, - backend->size); - close(fd); - return false; - } - + /* Let's do the same as memory-backend-ram,share=on would do. */ + name = host_memory_backend_get_name(backend); ram_flags = RAM_SHARED; ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; - - return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), - backend_name, backend->size, - ram_flags, fd, 0, errp); + return memory_region_init_ram_flags_nomigrate(&backend->mr, OBJECT(backend), + name, backend->size, + ram_flags, errp); } static void diff --git a/system/physmem.c b/system/physmem.c index dc1db3a384..4d331b3828 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -2057,6 +2057,59 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, } #endif +static int qemu_shm_alloc(size_t size, Error **errp) +{ + g_autoptr(GString) shm_name = g_string_new(NULL); + int fd, oflag, cur_sequence; + static int sequence; + mode_t mode; + + cur_sequence = qatomic_fetch_inc(&sequence); + + /* + * Let's use `mode = 0` because we don't want other processes to open our + * memory unless we share the file descriptor with them. + */ + mode = 0; + oflag = O_RDWR | O_CREAT | O_EXCL; + + /* + * Some operating systems allow creating anonymous POSIX shared memory + * objects (e.g. FreeBSD provides the SHM_ANON constant), but this is not + * defined by POSIX, so let's create a unique name. + * + * From Linux's shm_open(3) man-page: + * For portable use, a shared memory object should be identified + * by a name of the form /somename;" + */ + g_string_printf(shm_name, "/qemu-" FMT_pid "-shm-%d", getpid(), + cur_sequence); + + fd = shm_open(shm_name->str, oflag, mode); + if (fd < 0) { + error_setg_errno(errp, errno, + "failed to create POSIX shared memory"); + return false; + } + + /* + * We have the file descriptor, so we no longer need to expose the + * POSIX shared memory object. However it will remain allocated as long as + * there are file descriptors pointing to it. + */ + shm_unlink(shm_name->str); + + if (ftruncate(fd, size) == -1) { + error_setg_errno(errp, errno, + "failed to resize POSIX shared memory to %" PRIu64, + size); + close(fd); + return false; + } + + return fd; +} + static RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size, void (*resized)(const char*, @@ -2084,12 +2137,26 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size, new_block->used_length = size; new_block->max_length = max_size; assert(max_size >= size); - new_block->fd = -1; + new_block->guest_memfd = -1; new_block->page_size = qemu_real_host_page_size(); - new_block->host = host; new_block->flags = ram_flags; - ram_block_add(new_block, &local_err); + new_block->host = host; + + if ((ram_flags & RAM_PREALLOC) || !(ram_flags & RAM_SHARED)) { + new_block->fd = -1; + } else { + /* + * We want anonymous shared memory, similar to MAP_SHARED|MAP_ANON; but + * some users want the fd. So let's allocate shm explicitly, which will + * give us the fd. + */ + assert(!host); + new_block->fd = qemu_shm_alloc(new_block->max_length, &local_err); + } + if (!local_err) { + ram_block_add(new_block, &local_err); + } if (local_err) { g_free(new_block); error_propagate(errp, local_err); -- 2.47.0 Then, you only need a machine option to say "anon-shared", to make all anonymous memory sharable between processes. All it would do is setting the RAM_SHARED flag in qemu_ram_alloc_internal() when reasonable (!(ram_flags & RAM_PREALLOC)). To handle "memory-backend-ram,share=off", can we find a way to bail out if memory-backend-ram,share=off was used while the machine option "anon-shared" would be active? Or just document that the "anon-shared" will win? Alternatives might be a RAM_PFORCE_PRIVATE flag, set by the memory backend. With above change, we could drop the "bool share" flag from, qemu_anon_ram_alloc(), as it would be unused. [1] https://patchwork.kernel.org/project/qemu-devel/patch/20180201205511.19198-2-marcel@redhat.com/ -- Cheers, David / dhildenb