From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 4912027EC87 for ; Tue, 4 Mar 2025 15:51:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741103496; cv=none; b=g9Lv3WMtDv4y8ojoeQr4BeCdaBjCiSnlFLDGNbJiW6hw5Lnc47vo5elD0XFW8v1vuH1K4X/qyMAWJzh5YRN4pfduBJP4Jh7fpRnkSj6unMJtov8Sd0nZb3KAb6O/h/rFSE/VlppxPgb9UhwcP0Jpk8cQaBjkBc7n+7Ev+qGKYdI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741103496; c=relaxed/simple; bh=SO8mydmZaQBmGHqkXm7nBWI/I8sW6KvltUItc+vR0F4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CXJJ79x2Yzx9r+JvJuB5nmPpgsWIpQ1VULJXLWql28EEbwj9lttvjRkZ2zsMS/dPAN2WWcSNiAwLsNsLFdfhgBNriVKi7cBsSflPW5LXNmv5LTanvi6U1/T7yTtpRzRKSa+6vAxjZ4k5UpwU1RojiOimcjaoQNv7FejfxPrazO4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ddAqSdXQ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ddAqSdXQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741103494; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=sn11KJZxds0ej1UosF1rLJ47UkMAak3JuCgvKoEZngM=; b=ddAqSdXQ9DvdwIrMIcT2hzQQjS/dbmcizW86WupA2+SGp+aa0Q/PvTLx4rgIOT8JvwknQr h94fu5rXfb+DshVn1dswDZ2tZ6EoKVzObWj16LdhDU5vfwXVEjYHGVCqHqRKttp28w4ytq qKPjQowP8cVuXxth/fkVDIV8iKztMro= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-656-xhDmqJLONbWwBfoJMRyUYg-1; Tue, 04 Mar 2025 10:51:21 -0500 X-MC-Unique: xhDmqJLONbWwBfoJMRyUYg-1 X-Mimecast-MFC-AGG-ID: xhDmqJLONbWwBfoJMRyUYg_1741103480 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-390f365274dso1782039f8f.0 for ; Tue, 04 Mar 2025 07:51:20 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741103480; x=1741708280; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=sn11KJZxds0ej1UosF1rLJ47UkMAak3JuCgvKoEZngM=; b=s4d2asU+eCLkbH/48/7iX8xaK1gNP3q/gFylD8QegspeuqOhVBH3OIYCmAURZVDM7r PSXdChQjM++EiHg24Nqi93YfnI1nd+pbbwsjwqI2/WWjiQF5KqnsG86EpZmc6mWCWYR9 h5w2bS1yIfGf1J0+LfW74zHjfdrPEtOWRuAHDO4e66jnW/P7kV5Fbe4MoSLToA1r22TF F2zKkB05AIpBucV9WO18Vs14EPBrHdFbPJncOBjpBsNAQSicIbOffEpIPiKgL8d7xWni zBmu4lctcTwEX4v1bwHqDr9+xJrotA8R3wmRa5FQ0XrG0zb/hATKnFPVxTxIstzU70/x orIg== X-Forwarded-Encrypted: i=1; AJvYcCVU+4y4w1QdV+luREnP439d1eeBhfE/isaXtU/TJmMTF4KHasE4aI1ryfZtM+InEPIvipGpfKBVwlR565Ar@vger.kernel.org X-Gm-Message-State: AOJu0YyepSnVqfoZkmV6LHm96/jIGnb+oW+bqXkrKwG81a88UxqWzby0 lQFabeo2tJpTEyI/339IOS40psBWkq9nMX+xEI0zu/7SDcLYDXTilunrRI1tyIAJkkpNH6GA3xv 9qxcx/e4gYKdA2U+zwsgQ0Q5n4eiezKeK4vfJgDY6khSdQGgDuo4UW33ZmqfU+OY= X-Gm-Gg: ASbGncuRT+5nOG+J2I4Nj+NeU2naJ/xnZM6pxMC9lVUibyZZoosjkMcenrQavUy7m0e ffGMfASb6gLBxQZtjd3u2SiE1H4Fp1sHNLNt1xVN7RdqwMufrIvLrKbpapfcWTCzPpfPjNpleNJ c1WMRxqliI/Q4zLEv6jhalcW16G1rfq5yF2RM6KNT0kqn3q0/QTcX553qMZ51Lc82g1MSxGCe+g GYDiR4CvRaeaYnoAEOassEkfVuJunuGp3r80dTR2LUR2cQIbRdZq21JSAFvwzPtP6qk7v+vNEkA NAISgaKfsiHzHUtbsvbKfxuLjYMimqw/dwvnWYyYvenaj7EwehazfK4aZT1XbfQRuWEz8A6B5KX UEgxdqpbDQWH2HeLgjitDGH4xSOqMZP17Z/QitJjshoA= X-Received: by 2002:a05:6000:144a:b0:391:bc8:564a with SMTP id ffacd0b85a97d-3911561aaeemr3168063f8f.22.1741103479800; Tue, 04 Mar 2025 07:51:19 -0800 (PST) X-Google-Smtp-Source: AGHT+IHBKRpR1ew37y+xSwqdiAEEYgp9jcG+1wVSkkDjUC24e/FeWlE3M4RoXhNkgSdEbUx9SQm6QA== X-Received: by 2002:a05:6000:144a:b0:391:bc8:564a with SMTP id ffacd0b85a97d-3911561aaeemr3168051f8f.22.1741103479428; Tue, 04 Mar 2025 07:51:19 -0800 (PST) Received: from ?IPV6:2003:cb:c736:1000:9e30:2a8a:cd3d:419c? (p200300cbc73610009e302a8acd3d419c.dip0.t-ipconnect.de. [2003:cb:c736:1000:9e30:2a8a:cd3d:419c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43bc38986cbsm68968655e9.35.2025.03.04.07.51.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Mar 2025 07:51:18 -0800 (PST) Message-ID: <9d04c204-cb9a-4109-977b-3d39b992c521@redhat.com> Date: Tue, 4 Mar 2025 16:51:16 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/5] KVM: guest_memfd: Enforce NUMA mempolicy using shared policy To: Sean Christopherson , Ackerley Tng Cc: Vlastimil Babka , shivankg@amd.com, akpm@linux-foundation.org, willy@infradead.org, pbonzini@redhat.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev, chao.gao@intel.com, bharata@amd.com, nikunj@amd.com, michael.day@amd.com, Neeraj.Upadhyay@amd.com, thomas.lendacky@amd.com, michael.roth@amd.com, tabba@google.com References: From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 04.03.25 16:30, Sean Christopherson wrote: > On Tue, Mar 04, 2025, Ackerley Tng wrote: >> Vlastimil Babka writes: >>>> struct shared_policy should be stored on the inode rather than the file, >>>> since the memory policy is a property of the memory (struct inode), >>>> rather than a property of how the memory is used for a given VM (struct >>>> file). >>> >>> That makes sense. AFAICS shmem also uses inodes to store policy. >>> >>>> When the shared_policy is stored on the inode, intra-host migration [1] >>>> will work correctly, since the while the inode will be transferred from >>>> one VM (struct kvm) to another, the file (a VM's view/bindings of the >>>> memory) will be recreated for the new VM. >>>> >>>> I'm thinking of having a patch like this [2] to introduce inodes. >>> >>> shmem has it easier by already having inodes >>> >>>> With this, we shouldn't need to pass file pointers instead of inode >>>> pointers. >>> >>> Any downsides, besides more work needed? Or is it feasible to do it using >>> files now and convert to inodes later? >>> >>> Feels like something that must have been discussed already, but I don't >>> recall specifics. >> >> Here's where Sean described file vs inode: "The inode is effectively the >> raw underlying physical storage, while the file is the VM's view of that >> storage." [1]. >> >> I guess you're right that for now there is little distinction between >> file and inode and using file should be feasible, but I feel that this >> dilutes the original intent. > > Hmm, and using the file would be actively problematic at some point. One could > argue that NUMA policy is property of the VM accessing the memory, i.e. that two > VMs mapping the same guest_memfd could want different policies. But in practice, > that would allow for conflicting requirements, e.g. different policies in each > VM for the same chunk of memory, and would likely lead to surprising behavior due > to having to manually do mbind() for every VM/file view. I think that's the same behavior with shmem? I mean, if you have two people asking for different things for the same MAP_SHARE file range, surprises are unavoidable. Or am I missing something? -- Cheers, David / dhildenb