From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM12-DM6-obe.outbound.protection.outlook.com (mail-dm6nam12on2054.outbound.protection.outlook.com [40.107.243.54]) (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 349AE1940B2 for ; Fri, 8 Nov 2024 17:05:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.243.54 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731085509; cv=fail; b=qzcsvGvaIzJKmTHevNiYv/LanKMg2iXLEkxi5ySPzH25Mw/2OPdkUdpP54a63DIARYQfQZyPufqPC5HUcolIHJ28d9TbB/8q3kPEKXsp5ov+wgd7tWyrPQBuKUvOKBZKrMgWQEYTd4R2mPoBRzSVJ2dJjlQuSdqdSwNTQhix5us= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731085509; c=relaxed/simple; bh=//uN02JBa2w1Rs/po+9aXDE/9/kIOy+mFQ9ApdaZpso=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=Y9yebBQ3BFWSJR9ysW2jvlPDLomm+YTDjxcasW4sLg9hsYBMKf4HF979CUqQJZ2D6B3vfEvqkrMKUz1da0ToQyZ5HKjXXgOY0B2JvtWnWPdCdAmBi/rMtrJ6IuP2fD7QLUojxVu9GYJSiwWNeFm+8JTAlcNreZyXFhyeOJ0DAcY= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=oWu07Yev; arc=fail smtp.client-ip=40.107.243.54 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) header.d=Nvidia.com header.i=@Nvidia.com header.b="oWu07Yev" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=SXQaXW4k3lPpGtHl8QkybTSt94vDykgS4Wyp+xKXysXbGX6lmXBJqJE76FZWQtE21ng+LzNmLa25udl4PyYs77472qsUoVGJI/36Ma9is39K1DOiLpa52H8GbkGMNHNDBUL1zj7y5uFX/QIepo5r0eApTKqS/oxgzAL3Qp2tzXHZ/B2zOSKZkMAcTIVxJB4vwJjnmDh9vJCuLserOavq50wvOa6gOVdz4glhUH/Ou2BGWVM0WdpRekqRuv8o2sWYyxoKDdqK74xchhIysEJJYv6m2dFlDa706rqvR5AMP+OtAJsqqlqf/cF5bT4TR/txaGY2Y8plb0nWzrz8GOsD3A== 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=//uN02JBa2w1Rs/po+9aXDE/9/kIOy+mFQ9ApdaZpso=; b=vA5nxlUDjsoHHjfujgS5SzqXcra0Yh1o+Wda2sMMVjcs/2uJ7tAVS9858ioQHN6i9mVdS0NpM1ILfVP65Qx7xrD91EDAOPUsmSdAyUFcYpA7FEUronG8vCpqv9mahwAK5sqaLuRxaXcLX6nEozY3tSg3SjSOT/JilSZP4xKQpCVXUKQ9z7K2R6xcMYj4YaoZ0+7ZRAfakNPDlPKugebzFM2KHgxr9gLnPNReoH9LDcHEQ7KZqVBFzuJt1wxOvMdhJil97Z7y25NnjQkqMaVTdlTRyT/uwNVhlbiydjNViKdt8vlE7Y91fI06fX+bAxe7rxYQ7t1KOx4DM2sYHF2Fnw== 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=//uN02JBa2w1Rs/po+9aXDE/9/kIOy+mFQ9ApdaZpso=; b=oWu07YevNfjUe+iQmEu/5qSBwgF2NLeFIHtjaC3M/1t7WSS8nTkBtaToVvHQ94IPVLBC22X9LOU9AAwyg0wvBoXgLjweaPYegbmhLcgkhcs7zEopLny8Gf8MiX4qV7Tsm+j/1TevT9y1AwaAkjMrMauY/LZbZWpAKgd1GToKOk5kh8DSIhINNserxKuuqFR7WQZJR1K2II9ffit7FocHyUssDwNxc3dOsrhHfVmjogZAA7yDhSOzra8v4+T/BW6YR9eV6ESXo8XFsM/p51ngl4q8kyn9e0+BLwdhD8x/SDZa6IQAz83RwEW5m4vx2zrwgSdraVxbwyyavHrbw46h6w== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from CH3PR12MB8659.namprd12.prod.outlook.com (2603:10b6:610:17c::13) by DS7PR12MB5861.namprd12.prod.outlook.com (2603:10b6:8:78::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8137.19; Fri, 8 Nov 2024 17:05:02 +0000 Received: from CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732]) by CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732%4]) with mapi id 15.20.8137.021; Fri, 8 Nov 2024 17:05:02 +0000 Date: Fri, 8 Nov 2024 13:05:01 -0400 From: Jason Gunthorpe To: Fuad Tabba Cc: linux-mm@kvack.org, kvm@vger.kernel.org, nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, david@redhat.com, rppt@kernel.org, jglisse@redhat.com, akpm@linux-foundation.org, muchun.song@linux.dev, simona@ffwll.ch, airlied@gmail.com, pbonzini@redhat.com, seanjc@google.com, willy@infradead.org, jhubbard@nvidia.com, ackerleytng@google.com, vannapurve@google.com, mail@maciej.szmigiero.name, kirill.shutemov@linux.intel.com, quic_eberman@quicinc.com, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk Subject: Re: [RFC PATCH v1 00/10] mm: Introduce and use folio_owner_ops Message-ID: <20241108170501.GI539304@nvidia.com> References: <20241108162040.159038-1-tabba@google.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241108162040.159038-1-tabba@google.com> X-ClientProxiedBy: MN2PR19CA0060.namprd19.prod.outlook.com (2603:10b6:208:19b::37) To CH3PR12MB8659.namprd12.prod.outlook.com (2603:10b6:610:17c::13) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB8659:EE_|DS7PR12MB5861:EE_ X-MS-Office365-Filtering-Correlation-Id: 6f8d0b6c-5c6a-4b68-0146-08dd00177c01 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|7416014|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?2++y7XEbcBiMfgOEs2XAaQZ5LW3CIKcw9p6kwu9Bzz83g4et4/VKPGnA8fYf?= =?us-ascii?Q?tj24DWehjABfDqVzQkp0h4Jq9R4IqcNHZ15jPUQNJcYKJBhXrYnXWlDXHV5y?= =?us-ascii?Q?0P4qCxbY3sKNdBHNoS7QPRfYOSSSqqgVY9ZcTCWKn+QS6tE5jUHDuDbYaumC?= =?us-ascii?Q?K6H9nccUC4aMD1gdKPqhGggU5tEQhls2ddGIxE6mXWerazmKAfPWaRdiDycc?= =?us-ascii?Q?mzbA/UNyyd1BXHrWXm61YBJ6DIpVZU5Pv5rNbbA7LnnpF8QNRm75NqYtkR1p?= =?us-ascii?Q?Fy+nGFrmPc1n/Zttp+m5Q/YvHIMwTsSpyNoV4rW5i5iZsZ9+DxXlzH+ajRc3?= =?us-ascii?Q?v75MU5iV9NXvaEZd5RrmWoQysg5YDCA2SCutYeUqDPShXuSlGNbafTNN+UkJ?= =?us-ascii?Q?gaF4mlc6JAvMfmkLF9D2CWkes3I3K6Ii41ciZcaTItLzKSvmy0RkSYG8eRQw?= =?us-ascii?Q?c2WapThAGSDVKzvGohz6DnGhjvRtUChA3U3dxqwpAJJtejkW5FoYqNV4/bHK?= =?us-ascii?Q?tYV1XAw7Z1ywqEcEKUqE3bVazGRYVhx+b5hWDlWoPsXoFSFlpNdNZyTxi9cx?= =?us-ascii?Q?bahtsEwZ7DXCDMp97OTJ2coV3k2XUszJ3rmfxPNPBKj5+q6+5wtv6N1zoabQ?= =?us-ascii?Q?r9O+V0GofbzOuPzfnmS4aOVPNrS9DvBi7VEKByIvPZDtQBohfnQSDGyqM8oY?= =?us-ascii?Q?J4fw4pvR3kJHf+ynyvJLowx0hJsEmMbB/Jzdk+lCYI67RgBc08dYCTty2Van?= =?us-ascii?Q?Wj+z2yNznSnbYmTMXiHcg+Tccpz/bGejZPf52NYfcpycJ8G1N/yWGXucDHRF?= =?us-ascii?Q?YekTufgP9tyEnay7Vl4oGtpyg4/E+Egx0FvnYGftTUhmTionda/S2n96aHJs?= =?us-ascii?Q?3Erkea9i0DKO49YygeT2vQTeEjgzPUrqHUkt6diHAdx+vp6A78F7Co7wOc0+?= =?us-ascii?Q?Ik1YDN0qi7I8Xqtcrni0xG7wFw4mZvgjBZAmF0ZRsfA+hrpW5oqTHwDw8fnY?= =?us-ascii?Q?XXcnnD3eFV09fPLRKFHS0vrDblsQ972UY+cWIBERnBQWkqHAntX+NFZKRLD0?= =?us-ascii?Q?Rv3bJnfXI/RCUXNt/bzRnWQh+fMZoJVRwJImwJReh57GafK0zbedF8hy5Wiy?= =?us-ascii?Q?zXZGBlFZUrtixAVSv2FMKVEjnkWDxy0fG3CKCxt4GrIe9U6hQHyNlLzPkftv?= =?us-ascii?Q?vhUKU/gllFZjS4HRKv7WmrBgM92Q49ruWKIGJyrZs/sfnLqyn0mqRxpFwrSS?= =?us-ascii?Q?S5wkMaSUCctr0I21oBXSCZvpjR5wvN6Rz38stIU6GpAzUHPJVEa5GTRL+wF3?= =?us-ascii?Q?MO59Tpvri8OxEemThy8ioW1M?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH3PR12MB8659.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(1800799024)(7416014)(376014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?5+C2GjXByB1c8oXSDkfF20PxgCkwnUUP9MzJma1eOBupn0MG7y3CIEFpt1vX?= =?us-ascii?Q?Q6F8vY11EhxpZ6///1Y1vPw82a3Bl98bw6dFklAvRopU98fRHa6GIswp+cnD?= =?us-ascii?Q?oh4LuBzoWGF8gKGup1wrCqOnsp4GnDFoxGQnIUMq3+zY1d+q9fSRk9sixr7/?= =?us-ascii?Q?77//xM4d8F7os3vn8F80S/6HAXojX24HVnU9UNjKLpNrBzrLfOb+pVRbgUj+?= =?us-ascii?Q?D7dL2NViffYyI6t3FE1/eeEdCddmABjXwKTdBrX1zxR3D/bl6kp4EIRrdQrJ?= =?us-ascii?Q?fTd/6yGQveBAAEDK+u7LUIXY1AcM9ao2AXYxWGE98BDvTFVPuII4EAMsev+b?= =?us-ascii?Q?cY4XJflf+mRDTI/9fEAJbutAzmVWIZNLV28DmgEKlsGshPGp3a9j5bk9h0ZS?= =?us-ascii?Q?ErBKmRxgyQMTTCjyMD8bIYBllA1hXiHWwSS4SwEQATdwan4xtSzLL+yA49kO?= =?us-ascii?Q?tofpLG/IJ6cRkKKqZF4NnOs6OoPhtkzrJKT0DKnoncM+bJ/FLDgRkwGJ7N+k?= =?us-ascii?Q?UL5SEXiLuLZl1VRpxjRsS0DMz30JaHyakkMbPLYBLj0wVwQl+CrKeknptS+j?= =?us-ascii?Q?ZUHa5iTujhqt8bGoujFamUmg52sjMx7KXjCx617ZLhZHzwcF1c4CMlJ4hl22?= =?us-ascii?Q?WJuCOlsjkxFAZje+1ZmE4S1nahTWkGPYjkG8NTq0q2tmOZjjR3bkSXeGo5jP?= =?us-ascii?Q?4ZGu+i9hLlOpgvDSOznvFdEqbLTcaJVTkhKBNMNNicsToWnX6tfQcJ0iTL83?= =?us-ascii?Q?Yazv11W2ZyPAW6EVM0l/1Hr5l8C2dB5nxuolr5oZuR7mKe4M7ZDlyYEpkcAR?= =?us-ascii?Q?iPIIIfUOgAeFIjvRez/gm9TPFrlUBag5awkz/+Ns3ijXGpKGubJjdExCOhtk?= =?us-ascii?Q?v+wX+ohQpn+KKoJBPO8gTi/9FcxvFDbbs2gPKYqbu790MVLz0ZLKWNd+6QdO?= =?us-ascii?Q?h42d1yL2sZ5Gl6HORqbix+EMxnQi3u0CK2AFUPE8OVWjdOsiLi5RL/rgVtyR?= =?us-ascii?Q?g44TeiQpZV08voaaHdcIT36Xu2TEQz0Onii60IZ5J5hiYneFL5JAEhAapJ2l?= =?us-ascii?Q?uGCU1fSFVNRr3Z43yxzuxzUaXer7dpepVHcSsbcwjB/gRk3iNt3U0oB8+aoQ?= =?us-ascii?Q?FLtH4WXSKa809/k1zeOZlrLsC2ByDr249K0O1jplrH3/5WUlfMb9pGxHN130?= =?us-ascii?Q?XixOgbDmC6E8I7ZILMFvOx3RachHlDtt4VfyjcZPFnPe4E/OtEUwFqBAdTTR?= =?us-ascii?Q?+1CUfdS8M3GQOJrBUNxCDEoHU64xCW/d2tdwd+xblGs8aVHUgHLx41M47u5F?= =?us-ascii?Q?XB1Wy5D5SjzV4xOKAoAIM4bicLUdKLDUPgkrSfjwjH0ibHONOoEyn+341Kp8?= =?us-ascii?Q?HzoCDvsXghMJ+TTD18o85nx1LVzyzMZQ39KZBWta9YrOHxZ7AUOaPNNtE3yB?= =?us-ascii?Q?PpkwHwRnrZiv9g+y7cN97e7KP68HIb5Yi74DQbdEGNyO3LTv+zs86mhUc6yO?= =?us-ascii?Q?V+YchhgQ3iIp3JbRwvjbIAp36xDxV9NoKePAPOgUGrpGOe/CsmWxJeBPnCZ+?= =?us-ascii?Q?X6+HytxXPsigUeHevdvYMIvOvzPJm2Aw5+eUesHE?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6f8d0b6c-5c6a-4b68-0146-08dd00177c01 X-MS-Exchange-CrossTenant-AuthSource: CH3PR12MB8659.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Nov 2024 17:05:02.3076 (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: dI7yVwzkSnE2pVJPxwePzoViAy73wVhvzdYoTSaD/xDHbElb4TQ6XAvEe7bdPJoH X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB5861 On Fri, Nov 08, 2024 at 04:20:30PM +0000, Fuad Tabba wrote: > Some folios, such as hugetlb folios and zone device folios, > require special handling when the folio's reference count reaches > 0, before being freed. Moreover, guest_memfd folios will likely > require special handling to notify it once a folio's reference > count reaches 0, to facilitate shared to private folio conversion > [*]. Currently, each usecase has a dedicated callback when the > folio refcount reaches 0 to that effect. Adding yet more > callbacks is not ideal. Honestly, I question this thesis. How complex would it be to have 'yet more callbacks'? Is the challenge really that the mm can't detect when guestmemfd is the owner of the page because the page will be ZONE_NORMAL? So the point of this is really to allow ZONE_NORMAL pages to have a per-allocator callback? But this is also why I suggested to shift them to ZONE_DEVICE for guestmemfd, because then you get these things for free from the pgmap. (this is not a disagreement this is a valid solution, but a request you explain much more about what it is you actually need and compare it with the other existing options) Jason