From patchwork Thu Aug 29 22:24:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Elliot Berman X-Patchwork-Id: 13783971 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0AA1B1BA86D; Thu, 29 Aug 2024 22:24:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.168.131 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724970277; cv=none; b=klcEv4iy9ueVdjt4fzwfaJFtAZYCbB2gqw6VrquC5f2PcO7CA9bjtGlwqnvk7sU6ekQjcC47g579qlRLgR+BIft38Yp4KiC0VSWfQTCjtXx7UFz+Zk7bZaAuGqs6slWmCWXgiwgDQ+nNAI1XUxANFvThIANTuHZDzHz0A2A8f+E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724970277; c=relaxed/simple; bh=JFiV4jG07K1U1tQP1F+UO+KbTnuHVESnTnQYsb4NNmE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-ID:References: In-Reply-To:To:CC; b=HgPtiut10OzTwt9gq0FnXNWo0xn3Ikmf3OMEwlX5BW0zfx4ImfMHxUzS02DY//vrT+jPDPU37cQ82A0nca/XX8OEZlwHmEfvJ/YhXjTsQPRJGLc6ICFoifaT8nWBYMskMmfdqIprffX+GAfhu25UdP+Xhw5hn7UhCLyD7AluvSs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=quicinc.com; spf=pass smtp.mailfrom=quicinc.com; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b=fM2sBu6R; arc=none smtp.client-ip=205.220.168.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=quicinc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=quicinc.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b="fM2sBu6R" Received: from pps.filterd (m0279867.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 47THw8rh019432; Thu, 29 Aug 2024 22:24:14 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= nqQKk6MOQFV+1+R4/XWf2oHD5kh81okffsDtSVIGLYM=; b=fM2sBu6RSAMa+ucj chXJ2MezexBJDEBCe/1qL3cvNUY38wxUpB840yteHKfkLEtg+rmzWTVHaTPZPZDs 9lFDjTsCSD2R9C4P0eLlBMp8QeB2Fk6GFvXj8b8F6RPJ/DTwgrERrbtJejUYUG46 B5rXXJlJmNctWJpmTZYM37VyeP5YEKq+G+Kv6rn8lC0X8fBBkUun/avqj308QRK0 WY9ALgZjDJGr96vtS26rOpacPGJ9OG5q31ntkRPb1d6cqZ6SendYtAMCWMMKvcny XvcnI+HZWGzbxJFZZZ4QGInrsZzV193YMdFePOc0RKx9QhA2zNSecMavVvbTVGwz XcJodA== Received: from nasanppmta04.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 419putpu29-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 29 Aug 2024 22:24:13 +0000 (GMT) Received: from nasanex01b.na.qualcomm.com (nasanex01b.na.qualcomm.com [10.46.141.250]) by NASANPPMTA04.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 47TMODPG023594 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 29 Aug 2024 22:24:13 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Thu, 29 Aug 2024 15:24:12 -0700 From: Elliot Berman Date: Thu, 29 Aug 2024 15:24:12 -0700 Subject: [PATCH RFC v2 4/5] mm: guest_memfd: Add ability for userspace to mmap pages Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20240829-guest-memfd-lib-v2-4-b9afc1ff3656@quicinc.com> References: <20240829-guest-memfd-lib-v2-0-b9afc1ff3656@quicinc.com> In-Reply-To: <20240829-guest-memfd-lib-v2-0-b9afc1ff3656@quicinc.com> To: Andrew Morton , Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Fuad Tabba , David Hildenbrand , Patrick Roy , , Ackerley Tng , Mike Rapoport , , "H. Peter Anvin" CC: , , , , , Elliot Berman X-Mailer: b4 0.14.1 X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: YoBcGu8s-izQ3-pSoL8-J8hiQQsRjEyp X-Proofpoint-ORIG-GUID: YoBcGu8s-izQ3-pSoL8-J8hiQQsRjEyp X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-08-29_06,2024-08-29_02,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 phishscore=0 adultscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 suspectscore=0 spamscore=0 bulkscore=0 mlxlogscore=882 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2408290158 "Inaccessible" and "accessible" state are properly tracked by the guest_memfd. Userspace can now safely access pages to preload binaries in a hypervisor/architecture-agnostic manner. Signed-off-by: Elliot Berman --- mm/guest_memfd.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/mm/guest_memfd.c b/mm/guest_memfd.c index 62cb576248a9d..194b2c3ea1525 100644 --- a/mm/guest_memfd.c +++ b/mm/guest_memfd.c @@ -279,6 +279,51 @@ int guest_memfd_make_inaccessible(struct folio *folio) } EXPORT_SYMBOL_GPL(guest_memfd_make_inaccessible); +static vm_fault_t gmem_fault(struct vm_fault *vmf) +{ + struct file *file = vmf->vma->vm_file; + struct guest_memfd_private *private; + struct folio *folio; + + folio = guest_memfd_grab_folio(file, vmf->pgoff, GUEST_MEMFD_GRAB_ACCESSIBLE); + if (IS_ERR(folio)) + return VM_FAULT_SIGBUS; + + vmf->page = folio_page(folio, vmf->pgoff - folio_index(folio)); + + /** + * Drop the safe and accessible references, the folio refcount will + * be preserved and unmap_mapping_folio() will decrement the + * refcount when converting to inaccessible. + */ + private = folio_get_private(folio); + atomic_dec(&private->accessible); + atomic_dec(&private->safe); + + return VM_FAULT_LOCKED; +} + +static const struct vm_operations_struct gmem_vm_ops = { + .fault = gmem_fault, +}; + +static int gmem_mmap(struct file *file, struct vm_area_struct *vma) +{ + const struct guest_memfd_operations *ops = file_inode(file)->i_private; + + if (!ops->prepare_accessible) + return -EPERM; + + /* No support for private mappings to avoid COW. */ + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) != + (VM_SHARED | VM_MAYSHARE)) + return -EINVAL; + + file_accessed(file); + vma->vm_ops = &gmem_vm_ops; + return 0; +} + static long gmem_punch_hole(struct file *file, loff_t offset, loff_t len) { struct inode *inode = file_inode(file); @@ -390,6 +435,7 @@ static int gmem_release(struct inode *inode, struct file *file) static const struct file_operations gmem_fops = { .open = generic_file_open, .llseek = generic_file_llseek, + .mmap = gmem_mmap, .release = gmem_release, .fallocate = gmem_fallocate, .owner = THIS_MODULE,