From nobody Thu Sep 19 00:55:00 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1720047060; cv=none; d=zohomail.com; s=zohoarc; b=YqTHOk+Cd+S5Znkg/4aqnW5fYxR8wp8mxS5qw5oOpIi7o+WL0K94OMlqfebFiFfveM26muikrfV28I9QTt1soUqMXbvzwVbH7bfNOKyamo7r4VcJHFJaUOM5kap/yiWDM2jWh4fS3nyLMfv9Rtts1bBwhEwK1i9TfHILC0yqXPA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1720047060; h=Content-Type:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=nT/3bEAHv/ccVmumWuUDEQosc383NR5xwSBkJ1pU+nE=; b=Fq9D53xX/zJ0NjMj33vkkOTuLidM8SpkcObUSPCyrQZNjY0klx1fmHkiL5+MLeNjf9neGasG2fxHGIDUR7o18mMj+WjO2ZCKZ8N6qHA/FmeHdZnZhErnIMPYG6i77qiTUoGCWWDEcDxBfDaYw2ykqnJwjHQGVdi3ZpxbkBEFj+Y= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1720047060335830.1440361833967; Wed, 3 Jul 2024 15:51:00 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sP8mE-0000oa-5H; Wed, 03 Jul 2024 18:48:38 -0400 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 1sP8mC-0000nd-7g for qemu-devel@nongnu.org; Wed, 03 Jul 2024 18:48:36 -0400 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 1sP8mA-0004Wp-6m for qemu-devel@nongnu.org; Wed, 03 Jul 2024 18:48:35 -0400 Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-307-SlvQhxRHMW-1ez-uEx0UAQ-1; Wed, 03 Jul 2024 18:48:32 -0400 Received: by mail-ed1-f69.google.com with SMTP id 4fb4d7f45d1cf-586c45fc092so2782291a12.3 for ; Wed, 03 Jul 2024 15:48:32 -0700 (PDT) Received: from redhat.com ([2a0d:6fc7:441:91a8:a47d:5a9:c02f:92f2]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-58d50c4dad9sm1055799a12.10.2024.07.03.15.48.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jul 2024 15:48:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1720046913; 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: in-reply-to:in-reply-to:references:references; bh=nT/3bEAHv/ccVmumWuUDEQosc383NR5xwSBkJ1pU+nE=; b=RHl8IGDYJN9icaZQR0xdEGEYlB+PT2bfOIt9pzBRHmJkpDkdW7F77kTDbkGmxu5iKxYYoy 6vctobn6CEYJML8G+f7BHtFdets7RPMZD/uxjLwQBGbwUVIk6ZKEdaapRsw9e4aKd6GcK/ II8v9qOQQ1cWXvXbQxSoPB65oWrpoAo= X-MC-Unique: SlvQhxRHMW-1ez-uEx0UAQ-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720046911; x=1720651711; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=nT/3bEAHv/ccVmumWuUDEQosc383NR5xwSBkJ1pU+nE=; b=e5DtawXizb+a5jsVvNcB1ylEBabxWn2HTX/UIG89qkw/kErQ5GtfQ/DFAiCag+txjP CKZeDwxYdxC5JXsq/70juwjgTqfn9YkthNlBHrLdL8Wr3zLDR63Va4nJ+uj3RHnwDRy7 oFcYCo9/IpzXWnz3rdE8IB1CUqB2Wk7oHpHIMzVFJcPtqOwsqkpAMF92tdu7dathkzte ITnDkb8rw9hpVE4lwb4ZSuBx7wZPCMuIsLXgkVyP0qMCPQHBpbDdDCvHjqdOXBddWOhA eV7iMfb6ZdukL9oZKCC36l27qQHSioVFBqf9VoXaThlINszqJCS4FfNJyqgtTa+q1z1J tSzQ== X-Gm-Message-State: AOJu0Yz256Po6xQG2/jO6Y403xOFGZko3RVdyeXf/FuAwMWXXQoxKxH5 siBRG6FI7bveYyrgoEVsK1ibnRv3BbmWS/aP8FnyencV3+2f07FhMW0j9GWXlGc66uYT7Qqy5Aa Vwj/5EFF7aCCZS7Oc/UFTW6eouKZIkJLPTNLCisF2D1gd3/omPDlI3v25HeVHmb/qmDnevdtsyv zTlJjxaVw5pMfxxwqzxkDL1H6xM15IuQ== X-Received: by 2002:a05:6402:354c:b0:57c:a77d:a61e with SMTP id 4fb4d7f45d1cf-5879ede2779mr9469304a12.7.1720046910827; Wed, 03 Jul 2024 15:48:30 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH1CpDi8g8001mRuuRomIjteSgUp7J9coi8GeJJUJynn3T0HgEETgOZoox3ES71S7fZBZKSzg== X-Received: by 2002:a05:6402:354c:b0:57c:a77d:a61e with SMTP id 4fb4d7f45d1cf-5879ede2779mr9469265a12.7.1720046909788; Wed, 03 Jul 2024 15:48:29 -0700 (PDT) Date: Wed, 3 Jul 2024 18:48:24 -0400 From: "Michael S. Tsirkin" To: qemu-devel@nongnu.org Cc: Peter Maydell , Stefano Garzarella , David Hildenbrand , Stefan Hajnoczi , Markus Armbruster , Igor Mammedov , Paolo Bonzini , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , Eduardo Habkost , Eric Blake Subject: [PULL v3 53/85] hostmem: add a new memory backend based on POSIX shm_open() Message-ID: <4e647fa08586a5ada74cf6d3ae1cdf3a027202cb.1720046570.git.mst@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1720047062177100011 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Stefano Garzarella shm_open() creates and opens a new POSIX shared memory object. A POSIX shared memory object allows creating memory backend with an associated file descriptor that can be shared with external processes (e.g. vhost-user). The new `memory-backend-shm` can be used as an alternative when `memory-backend-memfd` is not available (Linux only), since shm_open() should be provided by any POSIX-compliant operating system. This backend mimics memfd, allocating memory that is practically anonymous. In theory shm_open() requires a name, but this is allocated for a short time interval and shm_unlink() is called right after shm_open(). After that, only fd is shared with external processes (e.g., vhost-user) as if it were associated with anonymous memory. In the future we may also allow the user to specify the name to be passed to shm_open(), but for now we keep the backend simple, mimicking anonymous memory such as memfd. Acked-by: David Hildenbrand Acked-by: Stefan Hajnoczi Acked-by: Markus Armbruster (QAPI schema) Signed-off-by: Stefano Garzarella Message-Id: <20240618100519.145853-1-sgarzare@redhat.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- qapi/qom.json | 23 +++++- backends/hostmem-shm.c | 123 +++++++++++++++++++++++++++++ backends/meson.build | 1 + docs/system/devices/vhost-user.rst | 5 +- qemu-options.hx | 16 ++++ 5 files changed, 164 insertions(+), 4 deletions(-) create mode 100644 backends/hostmem-shm.c diff --git a/qapi/qom.json b/qapi/qom.json index 9b8f6a7ab5..92b0fea76c 100644 --- a/qapi/qom.json +++ b/qapi/qom.json @@ -601,8 +601,8 @@ # # @share: if false, the memory is private to QEMU; if true, it is # shared (default false for backends memory-backend-file and -# memory-backend-ram, true for backends memory-backend-epc and -# memory-backend-memfd) +# memory-backend-ram, true for backends memory-backend-epc, +# memory-backend-memfd, and memory-backend-shm) # # @reserve: if true, reserve swap space (or huge pages) if applicable # (default: true) (since 6.1) @@ -721,6 +721,21 @@ '*hugetlbsize': 'size', '*seal': 'bool' } } =20 +## +# @MemoryBackendShmProperties: +# +# Properties for memory-backend-shm objects. +# +# This memory backend supports only shared memory, which is the +# default. +# +# Since: 9.1 +## +{ 'struct': 'MemoryBackendShmProperties', + 'base': 'MemoryBackendProperties', + 'data': { }, + 'if': 'CONFIG_POSIX' } + ## # @MemoryBackendEpcProperties: # @@ -1049,6 +1064,8 @@ { 'name': 'memory-backend-memfd', 'if': 'CONFIG_LINUX' }, 'memory-backend-ram', + { 'name': 'memory-backend-shm', + 'if': 'CONFIG_POSIX' }, 'pef-guest', { 'name': 'pr-manager-helper', 'if': 'CONFIG_LINUX' }, @@ -1121,6 +1138,8 @@ 'memory-backend-memfd': { 'type': 'MemoryBackendMemfdPropertie= s', 'if': 'CONFIG_LINUX' }, 'memory-backend-ram': 'MemoryBackendProperties', + 'memory-backend-shm': { 'type': 'MemoryBackendShmProperties', + 'if': 'CONFIG_POSIX' }, 'pr-manager-helper': { 'type': 'PrManagerHelperProperties', 'if': 'CONFIG_LINUX' }, 'qtest': 'QtestProperties', diff --git a/backends/hostmem-shm.c b/backends/hostmem-shm.c new file mode 100644 index 0000000000..374edc3db8 --- /dev/null +++ b/backends/hostmem-shm.c @@ -0,0 +1,123 @@ +/* + * QEMU host POSIX shared memory object backend + * + * Copyright (C) 2024 Red Hat Inc + * + * Authors: + * Stefano Garzarella + * + * This work is licensed under the terms of the GNU GPL, version 2 or late= r. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "sysemu/hostmem.h" +#include "qapi/error.h" + +#define TYPE_MEMORY_BACKEND_SHM "memory-backend-shm" + +OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendShm, MEMORY_BACKEND_SHM) + +struct HostMemoryBackendShm { + HostMemoryBackend parent_obj; +}; + +static bool +shm_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) +{ + g_autoptr(GString) shm_name =3D g_string_new(NULL); + g_autofree char *backend_name =3D 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"); + return false; + } + + if (!backend->share) { + error_setg(errp, "can't create shm backend with `share=3Doff`"); + return false; + } + + /* + * Let's use `mode =3D 0` because we don't want other processes to ope= n our + * memory unless we share the file descriptor with them. + */ + mode =3D 0; + oflag =3D O_RDWR | O_CREAT | O_EXCL; + backend_name =3D 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 =3D 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 lon= g as + * there are file descriptors pointing to it. + */ + shm_unlink(shm_name->str); + + if (ftruncate(fd, backend->size) =3D=3D -1) { + error_setg_errno(errp, errno, + "failed to resize POSIX shared memory to %" PRIu6= 4, + backend->size); + close(fd); + return false; + } + + ram_flags =3D RAM_SHARED; + ram_flags |=3D 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); +} + +static void +shm_backend_instance_init(Object *obj) +{ + HostMemoryBackendShm *m =3D MEMORY_BACKEND_SHM(obj); + + MEMORY_BACKEND(m)->share =3D true; +} + +static void +shm_backend_class_init(ObjectClass *oc, void *data) +{ + HostMemoryBackendClass *bc =3D MEMORY_BACKEND_CLASS(oc); + + bc->alloc =3D shm_backend_memory_alloc; +} + +static const TypeInfo shm_backend_info =3D { + .name =3D TYPE_MEMORY_BACKEND_SHM, + .parent =3D TYPE_MEMORY_BACKEND, + .instance_init =3D shm_backend_instance_init, + .class_init =3D shm_backend_class_init, + .instance_size =3D sizeof(HostMemoryBackendShm), +}; + +static void register_types(void) +{ + type_register_static(&shm_backend_info); +} + +type_init(register_types); diff --git a/backends/meson.build b/backends/meson.build index 106312f0c8..749b491f12 100644 --- a/backends/meson.build +++ b/backends/meson.build @@ -13,6 +13,7 @@ system_ss.add([files( if host_os !=3D 'windows' system_ss.add(files('rng-random.c')) system_ss.add(files('hostmem-file.c')) + system_ss.add([files('hostmem-shm.c'), rt]) endif if host_os =3D=3D 'linux' system_ss.add(files('hostmem-memfd.c')) diff --git a/docs/system/devices/vhost-user.rst b/docs/system/devices/vhost= -user.rst index 9b2da106ce..35259d8ec7 100644 --- a/docs/system/devices/vhost-user.rst +++ b/docs/system/devices/vhost-user.rst @@ -98,8 +98,9 @@ Shared memory object =20 In order for the daemon to access the VirtIO queues to process the requests it needs access to the guest's address space. This is -achieved via the ``memory-backend-file`` or ``memory-backend-memfd`` -objects. A reference to a file-descriptor which can access this object +achieved via the ``memory-backend-file``, ``memory-backend-memfd``, or +``memory-backend-shm`` objects. +A reference to a file-descriptor which can access this object will be passed via the socket as part of the protocol negotiation. =20 Currently the shared memory object needs to match the size of the main diff --git a/qemu-options.hx b/qemu-options.hx index 8ca7f34ef0..ad6521ef5e 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -5240,6 +5240,22 @@ SRST =20 The ``share`` boolean option is on by default with memfd. =20 + ``-object memory-backend-shm,id=3Did,merge=3Don|off,dump=3Don|off,shar= e=3Don|off,prealloc=3Don|off,size=3Dsize,host-nodes=3Dhost-nodes,policy=3Dd= efault|preferred|bind|interleave`` + Creates a POSIX shared memory backend object, which allows + QEMU to share the memory with an external process (e.g. when + using vhost-user). + + ``memory-backend-shm`` is a more portable and less featureful vers= ion + of ``memory-backend-memfd``. It can then be used in any POSIX syst= em, + especially when memfd is not supported. + + Please refer to ``memory-backend-file`` for a description of the + options. + + The ``share`` boolean option is on by default with shm. Setting it= to + off will cause a failure during allocation because it is not suppo= rted + by this backend. + ``-object iommufd,id=3Did[,fd=3Dfd]`` Creates an iommufd backend which allows control of DMA mapping through the ``/dev/iommu`` device. --=20 MST