From nobody Mon Mar 2 10:50:35 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; 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=fail(p=none dis=none) header.from=intel.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 177223084577916.329530807812944; Fri, 27 Feb 2026 14:20:45 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vw6Bj-00067Q-Py; Fri, 27 Feb 2026 17:20:01 -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 1vw6Bf-00066C-OV for qemu-devel@nongnu.org; Fri, 27 Feb 2026 17:19:55 -0500 Received: from mgamail.intel.com ([198.175.65.16]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vw6Be-0007n5-0w for qemu-devel@nongnu.org; Fri, 27 Feb 2026 17:19:55 -0500 Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Feb 2026 14:19:41 -0800 Received: from vkasired-desk2.fm.intel.com ([10.105.128.132]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Feb 2026 14:19:40 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1772230794; x=1803766794; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=H/a/kqUYjQO2m0ZdrAJtD1lUIdP2SDzEYOBTYhsibeI=; b=iXYIjKG93YTCeHLRBrV9A+ocvEKTcRqZXGrYXnI6fXSZmx6RkUrhUtpF nfwvLZnJFB8mS9aLEyqBa4lTCqcOpLiIO5LEIkQ9DiZlOs/qvwh3JmFTO RNq3fWnTDfE2CvAn9GfOITK0W5+/UNHowYZAPz7z9Y9rUiAih0E6pgJqS Q/escd7P46kUAG5IG1Ym4E2tWLkyCi/E0nfwfEMPX/8MSgIjpx7K2nSup LpP7xcNB7dfZLDIEBK41MOzDDg5X2fjVwm3vD9Aam+l4vafIP+ODy4aB3 2vut9QD/D73JYqpcxKmhdXF6OHoDipWEGE10DvlmN5qyxrmoWMAKTqUuk Q==; X-CSE-ConnectionGUID: kS9UaHqdTg6FXO19lrxYQA== X-CSE-MsgGUID: 0waavMFtRiO63bOvPTF1LA== X-IronPort-AV: E=McAfee;i="6800,10657,11714"; a="73509365" X-IronPort-AV: E=Sophos;i="6.21,314,1763452800"; d="scan'208";a="73509365" X-CSE-ConnectionGUID: 2d4HG9iqSiKiPWBofyEmtQ== X-CSE-MsgGUID: 3WcFRdvVRR+PhjZus5Zs8g== X-ExtLoop1: 1 From: Vivek Kasireddy To: qemu-devel@nongnu.org Cc: Vivek Kasireddy , Alex Williamson , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Subject: [PATCH v8 08/10] vfio/device: Add a helper to mmap a dmabuf Date: Fri, 27 Feb 2026 14:13:54 -0800 Message-ID: <20260227221632.827046-9-vivek.kasireddy@intel.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260227221632.827046-1-vivek.kasireddy@intel.com> References: <20260227221632.827046-1-vivek.kasireddy@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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=198.175.65.16; envelope-from=vivek.kasireddy@intel.com; helo=mgamail.intel.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 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_MED=-2.3, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.706, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.401, 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: qemu development 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-ZM-MESSAGEID: 1772230865843158500 In order to mmap a dmabuf, we first need to create a placeholder mapping that would fit the entire size of the dmabuf. This mapping would then be replaced with smaller mappings of individual dmabuf segments. Cc: Alex Williamson Cc: C=C3=A9dric Le Goater Signed-off-by: Vivek Kasireddy --- hw/vfio/device.c | 65 +++++++++++++++++++++++++++++++++++ hw/vfio/dmabuf-stubs.c | 7 ++++ include/hw/vfio/vfio-device.h | 17 +++++++++ 3 files changed, 89 insertions(+) diff --git a/hw/vfio/device.c b/hw/vfio/device.c index a25ecc3697..596fbceb68 100644 --- a/hw/vfio/device.c +++ b/hw/vfio/device.c @@ -728,3 +728,68 @@ int vfio_device_create_dmabuf_fd(struct iovec *iov, un= signed int iov_cnt, } return ret; } + +bool vfio_device_mmap_dmabuf(struct iovec *iov, unsigned int iov_cnt, + void **addr, size_t total_size, Error **errp) +{ + struct vfio_region_info *info =3D NULL; + VFIODevice *vbasedev =3D NULL; + ram_addr_t offset, len =3D 0; + RAMBlock *first_rb, *rb; + void *map, *submap; + int i, index; + + if (!vfio_device_lookup(iov, &vbasedev, errp)) { + return false; + } + + /* + * We first reserve a contiguous chunk of address space for the entire + * dmabuf, then replace it with smaller mappings that correspond to the + * individual segments of the dmabuf. + */ + map =3D mmap(NULL, total_size, PROT_NONE, MAP_SHARED | MAP_ANONYMOUS, = -1, 0); + if (map =3D=3D MAP_FAILED) { + error_setg_errno(errp, errno, "Could not reserve placeholder mappi= ng"); + return false; + } + + for (i =3D 0; i < iov_cnt; i++) { + rb =3D qemu_ram_block_from_host(iov[i].iov_base, false, &offset); + if (i =3D=3D 0) { + first_rb =3D rb; + } + if (!rb || rb !=3D first_rb) { + error_setg(errp, "Cannot mmap dmabuf with different regions\n"= ); + goto err; + } + + index =3D vfio_get_region_index_from_mr(rb->mr); + if (index < 0) { + error_setg(errp, "Cannot find region index for dmabuf segment\= n"); + goto err; + } + + if (vfio_device_get_region_info(vbasedev, index, &info)) { + error_setg(errp, "Cannot find region info for dmabuf segment\n= "); + goto err; + } + + submap =3D mmap(map + len, iov[i].iov_len, PROT_READ, + MAP_SHARED | MAP_FIXED, vbasedev->fd, + info->offset + offset); + if (submap =3D=3D MAP_FAILED) { + error_setg(errp, "Could not mmap dmabuf segment\n"); + goto err; + } + + len +=3D iov[i].iov_len; + } + *addr =3D map; + return true; +err: + munmap(map, total_size); + error_prepend(errp, "VFIO dmabuf mmap failed: "); + return false; +} + diff --git a/hw/vfio/dmabuf-stubs.c b/hw/vfio/dmabuf-stubs.c index e71e2b68dd..c3aa37233d 100644 --- a/hw/vfio/dmabuf-stubs.c +++ b/hw/vfio/dmabuf-stubs.c @@ -15,3 +15,10 @@ int vfio_device_create_dmabuf_fd(struct iovec *iov, unsi= gned int iov_cnt, error_setg(errp, "VFIO dmabuf support is not enabled"); return VFIO_DMABUF_CREATE_HOST_ERROR; } + +bool vfio_device_mmap_dmabuf(struct iovec *iov, unsigned int iov_cnt, + void **addr, size_t total_size, Error **errp) +{ + error_setg(errp, "VFIO mmap dmabuf support is not enabled"); + return false; +} diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h index 9dcf3ea57d..a1381f5f30 100644 --- a/include/hw/vfio/vfio-device.h +++ b/include/hw/vfio/vfio-device.h @@ -340,6 +340,23 @@ int vfio_get_region_index_from_mr(MemoryRegion *mr); */ int vfio_device_create_dmabuf_fd(struct iovec *iov, unsigned int iov_cnt, Error **errp); + +/** + * Mmap a dmabuf by first translating the addresses in the iovec + * array into VFIO region offsets and then creating a placeholder + * mapping that would be replaced later with mappings that + * correspond to the dmabuf segments. + * + * @iov: array of iovec entries associated with the dmabuf + * @iov_cnt: number of entries in the iovec array + * @addr: pointer to store the resulting mmap address + * @total_size: total size of the dmabuf + * @errp: pointer to Error*, to store an error if it happens. + * + * Returns true on success and false in case of an error. + */ +bool vfio_device_mmap_dmabuf(struct iovec *iov, unsigned int iov_cnt, + void **addr, size_t total_size, Error **errp); #endif =20 /* Returns 0 on success, or a negative errno. */ --=20 2.53.0