From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=pass header.oldest-pass=0 smtp.remote-ip=52.101.56.42 ARC-Seal: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=pass; t=1794600445; b=bhpwMqpZ7nkpFRPcvjc95VNI5z+8NQkvpN+COAjW6GmUYTXGHqX3VppeTBIW/sr6eZ4R M5SCbUgFmBqGCmZABpln9iZdiOaAYGTD7WDVBlw/pxlq8B2NFv3UgSmAP9h4vnyLpAY9R wuLyZn+J7XooKnuLP4aEnHLrqJ0BGOXYoTNx4zmwzC6Mn7S4lQZvY+C34zZgfb2EI0aNF xMdoYRhW1vMSR4QvK3bd9I3HcqmCGACyykOeWefnKGVYnt5hLzQcvv7KHhTUiMuRo8UAH 9GYoyy69A23L0rfe2N/amaQEY5G5aZAMDD0z835zYXQ7JdI99p7m2d2tIpGooALlTxQ== ARC-Message-Signature: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794600445; h=DMARC-Filter:DKIM-Signature:Received:Received:Date:From:To:Cc: Subject:Message-ID:References:Content-Type:Content-Disposition: In-Reply-To:X-ClientProxiedBy:MIME-Version:X-MS-PublicTrafficType: X-MS-TrafficTypeDiagnostic:X-MS-Office365-Filtering-Correlation-Id: X-MS-Exchange-SenderADCheck:X-MS-Exchange-AntiSpam-Relay: X-Microsoft-Antispam:X-Microsoft-Antispam-Message-Info: X-Forefront-Antispam-Report: X-MS-Exchange-AntiSpam-MessageData-ChunkCount: X-MS-Exchange-AntiSpam-MessageData-0:X-OriginatorOrg: X-MS-Exchange-CrossTenant-Network-Message-Id: X-MS-Exchange-CrossTenant-AuthSource:X-MS-Exchange-CrossTenant-AuthAs: X-MS-Exchange-CrossTenant-OriginalArrivalTime: X-MS-Exchange-CrossTenant-FromEntityHeader: X-MS-Exchange-CrossTenant-Id:X-MS-Exchange-CrossTenant-MailboxType: X-MS-Exchange-CrossTenant-UserPrincipalName: X-MS-Exchange-Transport-CrossTenantHeadersStamped; bh=msklUxZA1M+CX4sQQ8uuNswgev8L/HmjGBNvfeRpkLg=; b=E3fnLMmTyXJX/K5qGadJaUY8NgCI2Ms4aY54N62EEiMqkvkaqocWtt8cshF6RKX9Vj8W 8f3cXnJX4dzfaidHQJDHQtf3aQ13+PbLFKEe5/J7DTt0ftfvNoAj76HE+QWStOBhigQum ff8TjVszn1YzuRw7Y7wGfQCfRX18ShvCCYR2IfUCbgCTgpS8AWphy4rypZKSPW3KE06aS Tpz4OtCTIMZA0FYp/tMgvZj9eALwHN3PbqZZQQI3/PrjqB67TBG2D7fog0tiUxELo3lDL 9lnvOo7jimtF9O7VD6iOz++Mdg4N94BWOgrxKMHqa0WbtAKNvVJ2H/SYNI7xft5uZ0g== ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256 header.s=selector2 header.b=WHaqPg7m; arc=pass header.oldest-pass=0 smtp.remote-ip=52.101.56.42 Received: from BN1PR04CU002.outbound.protection.outlook.com (mail-eastus2azon11010042.outbound.protection.outlook.com [52.101.56.42]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (secp384r1) server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D17D606A333; Fri, 13 Nov 2026 20:07:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 8D17D606A333 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256 header.s=selector2 header.b=WHaqPg7m ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=NGkGhmI83qGW8G6xfelTrmpgNSqa3i+pOjrQIBZEfpMBXd4YBY6jtwc+v2PAjaJ0F9tsfgknOqsrnv9KM2QBkOTMubkDx6kiyUoikxIL1tEkxIbei13Kipx+jS7NjjCMnCoF/qw3zCM7JEXJ7RrCAELIOQFW2jbxzYHvhgehz284JAswsyIiijHaKULv67z1XKWtSTv9FjrC8e+zOM1tSdY73ylnRFvk/fFFK47bkfN2FiUa8E9jYm3I7dh7iiaAjohRhAow7ubqCJLYu4M1tVu6j7FRPBbMG6g/sZGuIWiHFrGT0Z0C7Af+U57ABXY98/+2fiVk6njFHTatR4rvfA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=msklUxZA1M+CX4sQQ8uuNswgev8L/HmjGBNvfeRpkLg=; b=TdAE2X5+uY67aIm0/GVyUFxzqGJmk8VPwu8K9QKV0TpElU2A1Ne9tqRt7tZkEvWl6ykDO6+8NmflE+HE9Z+wAnOGp57HJZCQHJcnFF0fb0ny6cYQ0j6JSVONrL6Ib7uddf/QojdT4HUZizJDm4KmcRUVANAu3YgfOhDbk8Hpg3Th+JiWpYNCqwNHhdR78oL6xEUSm8qn4fRLg0A4Qp8MjcCpZbUI/uqs017lTmBxLzhA0X7B+HKaNhMzI9k+AmT87qCsYfwQPy0CkW+PndqnEfeM5HQHs9DS3uvmAEggLKS5adVBClm0QuycgWD4qt+Yam4ppPxQoGX0+FUUHKGtCw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=msklUxZA1M+CX4sQQ8uuNswgev8L/HmjGBNvfeRpkLg=; b=WHaqPg7mSlbzaXHEZ2XmzXor1z4XSKzQ4mLckviSpdxv9DPwpqHNlIkhAFXVPfWGcS1JYQttJT/vlhVqO4VKtkcMe1BG9E1Va4KlZ3uUlsrscx0kSvkw+sg7npAL/IKfbRXkIF0fWP1YxY0Cdtuz/yCwI3GaE0Qk7lRBdFi9o956OqDqheFDIjv4SOXFqxLmX2T/K+XMyV0Gtv2uXjK/r8Y/j47JNdGzoa0B8bFKJWSUMETxgQvNmChS/cYopTvI0P9uG3/W3gUXAiIri7TUdk2PWd3miIKX+zZAtNbsJzDzuONCBR2eQHp+ADL8tR+6BTuVNJ/aoIo1TRuvMJxsiw== Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from CHBPR12MB731189.namprd12.prod.outlook.com (2603:10b6:610:33d::12) by BL1PR12MB5732.namprd12.prod.outlook.com (2603:10b6:208:387::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.615.9; Fri, 13 Nov 2026 20:03:05 +0000 Received: from CHBPR12MB731189.namprd12.prod.outlook.com ([fe80::b0e5:123d:fe06:e10d]) by CHBPR12MB731189.namprd12.prod.outlook.com ([fe80::b0e5:123d:fe06:e10d%6]) with mapi id 15.21.0615.009; Fri, 13 Nov 2026 20:03:05 +0000 Date: Fri, 13 Nov 2026 16:03:03 -0400 From: Jason Gunthorpe To: "Gregory Price (Meta)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, leon@kernel.org, akpm@linux-foundation.org, david@kernel.org, kas@kernel.org, dave.hansen@linux.intel.com, bp@alien8.de, rppt@kernel.org, stable@vger.kernel.org, "Lorenzo Stoakes (ARM)" Subject: Re: [PATCH] mm/hmm: reject shadow-stack mappings Message-ID: <20261113200303.GA395967@nvidia.com> References: <20261113195536.2660763-1-gourry@gourry.net> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261113195536.2660763-1-gourry@gourry.net> X-ClientProxiedBy: YT1PR01CA0061.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2e::30) To CHBPR12MB731189.namprd12.prod.outlook.com (2603:10b6:610:33d::12) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CHBPR12MB731189:EE_|BL1PR12MB5732:EE_ X-MS-Office365-Filtering-Correlation-Id: 92c70baa-a9e8-41cd-932f-08df41c12136 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014|23010399003|22082099003|18002099003|3023799007|56012099006|261026121527099003|10067099003|11063799006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CHBPR12MB731189.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(7416014)(23010399003)(22082099003)(18002099003)(3023799007)(56012099006)(261026121527099003)(10067099003)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?vIOpdomXA+76ySEZkQ1GnTlI+9acNpZ9Pm9E+3NKraI/h3TqD9gFHDSEej8f?= =?us-ascii?Q?k5hDpjdrsisMixW8s8KHNgC+cGc7lQltfpC0RKc1cs3tjODoYaTqWkgkKkWz?= =?us-ascii?Q?3tm0ZC+41zkU6QFO28pgMkO8XqDW65dKV0O8pjihMNsbAvTewPFARWrr7N1q?= =?us-ascii?Q?vhO/uRoxCL/KsiMwBjlBji72DdCMBKvrz/rfQjeg4LK/EgKZ1K5svInOfJG9?= =?us-ascii?Q?wY1HkIC7/doSB41vMgzVIe0YMhqDYV3NEQ+ZWaRt6yK4ZGb+mKPZL11XtMRj?= =?us-ascii?Q?JP9ZX91zMJfi7DAev8bSft9Stn9xIyPhVQhjVia9OKDX5cf7nESUTsZcYLUP?= =?us-ascii?Q?ZIQKWCNQ3Ix9Zs7Fe6/fenlRlYZysMYsrRbAcMeFYg6dOCI8vCZjfdBJlxsW?= =?us-ascii?Q?GdccHaf+FhiUsFtjrHnJyPUwenCXTOUUaiUpeC3CykDbncxhRRlbXvMTzpIG?= =?us-ascii?Q?geResm/m+6kiro9NhqxTkaI0Iza8cIomqGUNNo4arKEkFvL8f80IqRGKfZbB?= =?us-ascii?Q?z2Jn0GnjMnorrAT92hH9NXIUkxuvOfduXtUm7jTY5yO6YjQUBPwgYF4ucPaA?= =?us-ascii?Q?9cZVL62mp2fjUMj1C2y+NGxcCaBUvHmcdRcG15wdaLWmaiZ97/qWDustZhDq?= =?us-ascii?Q?rmPMZ5nQyGectIOn+qMe0zIZEcmU22pPy32Eij9B9tnaK9bOeAH4qXOFlrUo?= =?us-ascii?Q?mseIEzN4Z9b36fAkBGnB7WY6UB2Qu3Y2jQjGMOzcs8oojsatPWIe8PCnuJZM?= =?us-ascii?Q?VyeTauqY2sxa9Uo7PAzBP9JY6KlHJuw6O8RXBPDDqq86H1rPR9Vcian9GGDJ?= =?us-ascii?Q?agn1SCBb63NyjJo2ILFauS0p2DLRDkZtn7ot+1Wlj0m7zLD9uU3d0LZCCxKI?= =?us-ascii?Q?1UFoblZxZai+bqAn9BPYQRCJ795pp3sFyPr6+F9q0gFjpSSr5cdTV3fkQwLk?= =?us-ascii?Q?llBfMSckKXvZGH7reK7p7Ddl40CuD+ErJiee7HQ59MsmurfdDNIb20hkM3lR?= =?us-ascii?Q?pr6ExP3oGCHTdT6MWJAl7hzRQhO3AjA3iYBfH9y+blt8J42u7uPGS/ADi91z?= =?us-ascii?Q?tt0p8KXZlGbmeTOR9rcR88T776izlueKOsiSls/Fr+68h//kgdM3bs5S62UQ?= =?us-ascii?Q?CzY77cXhCHTHjrdqC8V5iy+/vLih6sYeTLq6uARu911J2bVKEhRpfdbrN7qw?= =?us-ascii?Q?prRGPkWDAIruNs3rASwz+g+Ys6gm/vuMRIKUjNHbhJcnGnFv7Z0lka2pDUNA?= =?us-ascii?Q?1C7OOWrFrg0ilScxscKyoLsXlKbBUBl1491vfCh0J85jZABwxTqFCQ9OzbUm?= =?us-ascii?Q?7Epn6Jy1kP3bPHsEfpDGU1MmXiXVxYn6FicPhTT1ls03LW4hSO8eSKhdI1da?= =?us-ascii?Q?TO6AoZ3DR74r91pxZi27VujUfoMZU9TIEOI+rS2cGE2GYPI2KtP5vbTTu/rN?= =?us-ascii?Q?a5t7Va8InUYv8JMaNq020sUZ2NVxwxItAtQoW+SJdcvvXcuri/QwP7o7tJxy?= =?us-ascii?Q?FeEo20bm/5543arfTI/cU82fak6vedC02DCG0D4TA/G65HhA+69IvUUKVMgN?= =?us-ascii?Q?JbUPCpjjUatr3I6wfHYE0cV8Q6rCe5MU6Y/EMWBU3HZO7xBk2MKmhOl64E6+?= =?us-ascii?Q?LPKpjJXFuZ2apcindUYfUixgPSFUjD3Sbvxbkw53e8kph/D8z/PPJUvYO42H?= =?us-ascii?Q?nvmNCJU21PmCpYJnJO5/GsKpi6q/y+1F+SNkiPLjwZ13k1q1?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 92c70baa-a9e8-41cd-932f-08df41c12136 X-MS-Exchange-CrossTenant-AuthSource: CHBPR12MB731189.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Nov 2026 20:03:05.3215 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: IQ9YVm30fvigh+aD9tF6cawEQZU3C2V2IVws70thKvtrySZNsaZDLfMfpXh5/8ug X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5732 On Fri, Nov 13, 2026 at 02:55:36PM -0500, Gregory Price (Meta) wrote: > HMM can grant ordinary device write access to a userspace shadow stack. > On x86, pte_write() is true for a shadow-stack PTE, so a populated page > can be returned with HMM_PFN_WRITE without taking a CPU write fault. I'm not sure I understand this? The pte is writable but you don't want only DMA to write to it? Is there something special on x86 that makes the shadow stack pte non-writable by the CPU? A few more words here would help Regardless, this seems reasonable to me, there is no use case to write to the shadow stack.. Reviewed-by: Jason Gunthorpe Jason