From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7014ECA1004 for ; Sat, 30 Aug 2025 16:16:45 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 82D2F10E340; Sat, 30 Aug 2025 16:16:44 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="YrNdQS83"; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id E840F10EC38 for ; Fri, 29 Aug 2025 19:58:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756497530; 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=xZo5kWZ4wC3wGmKqPk6eI0RfSbah2VPwvlM0503suW8=; b=YrNdQS83bJ1mO8ZxPPvgVBl8YBCjWkA5KjTR4CqiGaTB/d0iXH9Ci/we/Tflqg4pwG5q0c FErGvERXkz7FitX5GIRIlmHobjsD2ryJ/LR7nk/UhU3Ysqyvrks81BVX6WpYY8vHuaclS6 pbVfAltWZEg6bhL1V0wh7faZUSDJFD0= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-423-mmve1NaCPnSD5b7g_CGQcQ-1; Fri, 29 Aug 2025 15:58:43 -0400 X-MC-Unique: mmve1NaCPnSD5b7g_CGQcQ-1 X-Mimecast-MFC-AGG-ID: mmve1NaCPnSD5b7g_CGQcQ_1756497523 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-3cca50781ddso1056813f8f.2 for ; Fri, 29 Aug 2025 12:58:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756497523; x=1757102323; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :references:cc:to:from:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=xZo5kWZ4wC3wGmKqPk6eI0RfSbah2VPwvlM0503suW8=; b=xGnVqPCLXxZVFQ22YSHIFP2p9Q4gDrlrMhTK4HEzjHW9X5Y+6jfeSoeFZ5U8Kuq/df dr2MWTnBJ6ZwurAg1RxxRq19vtd/SNVIeQiHKTd4EnJjJFbJa0gqcJiaaekI3sjJjQXM SMJuk5N9/xkWxS1DdSSdR/Od84ndhhAw8t+0MbX9r+BkZ09dmeAoHOl1HJKgKYbqnb4H 3aLSofzJf05vrpumBBzUdm3R35b6R0zA8GRwWxeGJW06UGHbRX3z6vc7o0Ediu6knOke vkjBP+cMpes6oscPupF05HD88JDsHo0LspYBrlrf3759JJ+xmfLQ81nW8rqXBMEw81lE f/CQ== X-Forwarded-Encrypted: i=1; AJvYcCWn2UKR/ILqNF43rGuSgUjcs6g5uVgBdB/zisDVtswONMvpH1FigQyM1qf1GTBepSy4TSf6yeId@lists.freedesktop.org X-Gm-Message-State: AOJu0YxlITnbd7KMfEpCED9sb9G6QNBgZEHoQTDCPgPA7RIW1hIXAwoC GUXK6NVNoFlDqKh9raxlHRHsMiS9/sjI7pYimJlvbZTLp4zcz67wtuhdB/T0JsZNM3Dr1ynVg5G HZvVkLZlSOek91/L4kLxUm4btvcIGbzLQAmpjUxqGqdeN8gzwcAT4lljrSBxZ9kO+9o4= X-Gm-Gg: ASbGncsIGJ6bjLsJOYwk7x/g8AZ9A8n7IPkWyjMgK2AM7lfuXp4WAIzmTzVudNJ1CvE XT0Y7ClzfQAtDgE8gT6TgMk5JkM0vPxB+TVyb1NXZgUDYQgVnlrCA4brDKH9u8Fe/3Gu2akI7by NwM4hdFPVG62UmFxT/eRSKovZvsQR4y/lMd66DpXmKWnZ+0JV4C34Ju+dwuQPjkAtiC/158FIpT wt56+gR7KOeIAjhCUVRBJW0dD3nQAW5AP2L9zW4HdQJmhsCVjsprY1HFvk/pikRJXPTp31tHeWD PG517cL+rqfceaM2nkQ7Bass3Kqe9q8ChJpiXgAddynBWWfIQxUYDROZtG954N1Gzq2gKMGCX0m cEmxArBOdDugdvDuYIsjchqWBNaXV5puI24RRiwSioNNu+qwdNno17DWbkOycGzan X-Received: by 2002:a05:6000:40dd:b0:3a4:d6ed:8df8 with SMTP id ffacd0b85a97d-3c5dc734927mr22634461f8f.39.1756497522590; Fri, 29 Aug 2025 12:58:42 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEvHEkvHJSsvUdMiTLwAfagEik+QO+Eh4rmmPk5gnzbPICxQ2Th8mxXR7QyiTGZMb0BpkDB9Q== X-Received: by 2002:a05:6000:40dd:b0:3a4:d6ed:8df8 with SMTP id ffacd0b85a97d-3c5dc734927mr22634443f8f.39.1756497522163; Fri, 29 Aug 2025 12:58:42 -0700 (PDT) Received: from ?IPV6:2003:d8:2f1d:100:4f8e:bb13:c3c7:f854? (p200300d82f1d01004f8ebb13c3c7f854.dip0.t-ipconnect.de. [2003:d8:2f1d:100:4f8e:bb13:c3c7:f854]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf8a64fce8sm4236812f8f.34.2025.08.29.12.58.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 Aug 2025 12:58:41 -0700 (PDT) Message-ID: <46b99b0f-688d-4625-8b68-8176185ced43@redhat.com> Date: Fri, 29 Aug 2025 21:58:40 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: stupid and complicated PAT :) From: David Hildenbrand To: =?UTF-8?Q?Christian_K=C3=B6nig?= , intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, x86@kernel.org Cc: airlied@gmail.com, thomas.hellstrom@linux.intel.com, matthew.brost@intel.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, Lorenzo Stoakes References: <20250820143739.3422-1-christian.koenig@amd.com> <4e5f4ef0-53f1-417e-8f3b-76fd7c64cd23@amd.com> <6591105b-969d-44d6-80e1-233c1b84b121@redhat.com> <75aca34d-3557-49e9-a523-bd3244c28190@redhat.com> <87050572-811e-4b0c-9ebd-8ebb05f3c617@amd.com> <3a91d9df-1536-490b-bbc6-268a3a32ac1c@redhat.com> <00aaca69-2549-48b4-bd3c-fcebe2589df0@redhat.com> <094606f3-a138-4561-a0b7-d952f4896939@amd.com> <4ef6e251-37c2-47ac-bff7-3b2a7d7e58d6@redhat.com> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <4ef6e251-37c2-47ac-bff7-3b2a7d7e58d6@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: LjReR5ekx6o093RGYqOhMTgPoEDlQrWBaccAEWb5QZY_1756497523 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Sat, 30 Aug 2025 16:16:32 +0000 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On 29.08.25 21:52, David Hildenbrand wrote: > >> >> Yes, that can absolutely happen. But for iomem we would have an explicit call to ioremap(), ioremap_wc(), ioremap_cache() for that before anybody would map anything into userspace page tables. >> >> But thinking more about it I just had an OMFG moment! Is it possible that the PAT currently already has a problem with that? >> >> We had customer projects where BARs of different PCIe devices ended up on different physical addresses after a hot remove/re-add. >> >> Is it possible that the PAT keeps enforcing certain caching attributes for a physical address? E.g. for example because a driver doesn't clean up properly on hot remove? >> >> If yes than that would explain a massive number of problems we had with hot add/remove. > > The code is a mess, so if a driver messed up, likely everything is possible. > > TBH, the more I look at this all, the more WTF moments I am having. > >> >>>> What I am currently wondering is: assume we get a >>>> pfnmap_setup_cachemode_pfn() call and we could reliably identify whether >>>> there was a previous registration, then we could do >>>> >>>> (a) No previous registration: don't modify pgprot. Hopefully the driver >>>>       knows what it is doing. Maybe we can add sanity checks that the >>>>       direct map was already updated etc. >>>> (b) A previous registration: modify pgprot like we do today. >> >> That would work for me. >> >>>> System RAM is the problem. I wonder how many of these registrations we >>>> really get and if we could just store them in the same tree as !system >>>> RAM instead of abusing page flags. >>> >>> commit 9542ada803198e6eba29d3289abb39ea82047b92 >>> Author: Suresh Siddha >>> Date:   Wed Sep 24 08:53:33 2008 -0700 >>> >>>     x86: track memtype for RAM in page struct >>>         Track the memtype for RAM pages in page struct instead of using the >>>     memtype list. This avoids the explosion in the number of entries in >>>     memtype list (of the order of 20,000 with AGP) and makes the PAT >>>     tracking simpler. >>>         We are using PG_arch_1 bit in page->flags. >>>         We still use the memtype list for non RAM pages. >>> >>> >>> I do wonder if that explosion is still an issue today. >> >> Yes it is. That is exactly the issue I'm working on here. >> >> It's just that AGP was replaced by internal GPU MMUs over time and so we don't use the old AGP code any more but just call get_free_pages() (or similar) directly. > > Okay, I thought I slowly understood how it works, then I stumbled over > the set_memory_uc / set_memory_wc implementation and now I am *all > confused*. > > I mean, that does perform a PAT reservation. > > But when is that reservation ever freed again? :/ Ah, set_memory_wb() does that. It just frees stuff. It should have been called something like "reset", probably. -- Cheers David / dhildenb