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 BF767CA0FF7 for ; Wed, 27 Aug 2025 07:57:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D681010E75A; Wed, 27 Aug 2025 07:57:38 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="OdPAHhM8"; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id EA00310E640 for ; Tue, 26 Aug 2025 12:07:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756210075; 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=Uo8QqPtYPWcbg2SJ7UNAfQxo4xVeFqBTJ7SinpEUAHI=; b=OdPAHhM8CjTsJ3QBd1e4eBZrHCitCO6WtAMgNf1wYxmsclf7g3nfXmF3BnY+DTAWLigeBd JGVZhQJrdwf5PrY2NIC1tsEBAJEguvW+xbo4DJBT601D5Wn3dWSaGu0BzmeFfSTwdAT7Ot na37nXgg70iSm2EyF+BjGmRJygkwGq8= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-304-ItytC3faOIGWAT8dt_bfEw-1; Tue, 26 Aug 2025 08:07:54 -0400 X-MC-Unique: ItytC3faOIGWAT8dt_bfEw-1 X-Mimecast-MFC-AGG-ID: ItytC3faOIGWAT8dt_bfEw_1756210073 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-45a1b0bd6a9so30319565e9.2 for ; Tue, 26 Aug 2025 05:07:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756210073; x=1756814873; h=content-transfer-encoding:in-reply-to: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=Uo8QqPtYPWcbg2SJ7UNAfQxo4xVeFqBTJ7SinpEUAHI=; b=RcNHRWPWXoYisYIGGYJxSh/8OUJX3J0wM4wGFZdcNBSiA6sPMiDxzwKwjQSStQ38c2 3HfwQ3AznRNrigRYFxd9gY7j2W5UM5fFC1LBWA1H7m5vE5vRer9D4Ml8gyL64+hP++bZ Jh/FK31LIWbiPQjiwKAruX7NRggQLjOSDkurJa2MfEUHdckGxd9W96Baaom/i7Al60dZ Hj6H0Nkdrz1lYxmvRZ5cPJ5jPTC7pTSZW1vPwCIhFyjDC9lAptnuMZzpqn0K3Jm77Lbr llrKinBBFLCVNTZsXuVp1VaFmKZnLDChRfQ9cjOW+F+HaKuOId7EABrfPe0yOXzqtyFv scMA== X-Forwarded-Encrypted: i=1; AJvYcCVJszBAzcJA4uUR9UduXECrQqkcTGFj2E8E4bi5V3GKB/8Pl/4qq2uwXmqkCIXxrSZDTrPp0mG+@lists.freedesktop.org X-Gm-Message-State: AOJu0Yyj8dq+yDnj8swJ7pew2JMcxDFtewtUGD0+A1Ye97o6SHfjF4ue bzm+n2D9Ps9CBHgDTo4fG43HqNbafaG+YWcsl4uALQpvLbEg39i2HXv1bQssCPmKGtfTccPAxLK BZLHIx2yr2GmRPAtjTtNCfdT0Bb1Mvi38c9zyRK7xYYv68Gvrko11Nml1oLfKxC5mZW4= X-Gm-Gg: ASbGncsKym3HzhoItzZvMvJAftUZNA9D6zJnrp9AZ0szVF4+5ifzkKRgEdsSxeNGRqY jxIWfuzB9l3uBGb67mlJPLR8qcbdVxydm383b8xZ9JnRhkW7+0Xv57aEGVe8RYolKJZWp/wtkIF 9432unwr0O/vo6P84EGXwUtJtM12TE++59NwmgCW3zqqvNYw47YDSQUUJREEW0gwXM940MzCvJM 9tu1YqzsRCTO2Ak3Osc2WPe/lZKHUUSFxWQJqVIfmi6kwrqGupppEW0jtf7BEuiXl7YToYunQQQ lfaQnR23x6Da70qBGmXiaHrqvdHeO5+SjXO9kDZOnAIAHKemRrveaagtwgHMYxagqX1VlcSKNA= = X-Received: by 2002:a5d:4948:0:b0:3c6:af40:a774 with SMTP id ffacd0b85a97d-3c6af40aa2amr8520870f8f.22.1756210073135; Tue, 26 Aug 2025 05:07:53 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGph2EoUnVtafTDMODsVx9IZs4dFlfHWSAK/zJyh0p3gRtMg5bs99D6Y9j7BY5F1T/rMK8pCA== X-Received: by 2002:a5d:4948:0:b0:3c6:af40:a774 with SMTP id ffacd0b85a97d-3c6af40aa2amr8520837f8f.22.1756210072601; Tue, 26 Aug 2025 05:07:52 -0700 (PDT) Received: from ?IPV6:2a09:80c0:192:0:5dac:bf3d:c41:c3e7? ([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cbb710172fsm1709728f8f.48.2025.08.26.05.07.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Aug 2025 05:07:52 -0700 (PDT) Message-ID: Date: Tue, 26 Aug 2025 14:07:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: 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> From: David Hildenbrand 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: GAlYif0-1Ym-TFx7nBozoRHDcw21uEkMP4urzjoaNSk_1756210073 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: Wed, 27 Aug 2025 07:56:57 +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" >> >> 1) We use another interface that consumes pages instead of PFNs, like a >>    vm_insert_pages_pgprot() we would be adding. >> >>    Is there any strong requirement for inserting non-refcounted PFNs? > > Yes, there is a strong requirement to insert non-refcounted PFNs. > > We had a lot of trouble with KVM people trying to grab a reference to those pages even if the VMA had the VM_PFNMAP flag set. Yes, KVM ignored (and maybe still does) VM_PFNMAP to some degree, which is rather nasty. > >> 2) We add another interface that consumes PFNs, but explicitly states >>    that it is only for ordinary system RAM, and that the user is >>    required for updating the direct map. >> >>    We could sanity-check the direct map in debug kernels. > > I would rather like to see vmf_insert_pfn_prot() fixed instead. > > That function was explicitly added to insert the PFN with the given attributes and as far as I can see all users of that function expect exactly that. It's all a bit tricky :( > >> >> 3) We teach PAT code in pfnmap_setup_cachemode_pfn() about treating this >>    system RAM differently. >> >> >> There is also the option for a mixture between 1 and 2, where we get pages, but we map them non-refcounted in a VM_PFNMAP. >> >> In general, having pages makes it easier to assert that they are likely ordinary system ram pages, and that the interface is not getting abused for something else. > > Well, exactly that's the use case here and that is not abusive at all as far as I can see. > > What drivers want is to insert a PFN with a certain set of caching attributes regardless if it's system memory or iomem. That's why vmf_insert_pfn_prot() was created in the first place. I mean, the use case of "allocate pages from the buddy and fixup the linear map" sounds perfectly reasonable to me. Absolutely no reason to get PAT involved. Nobody else should be messing with that memory after all. As soon as we are talking about other memory ranges (iomem) that are not from the buddy, it gets weird to bypass PAT, and the question I am asking myself is, when is it okay, and when not. > > That drivers need to call set_pages_wc/uc() for the linear mapping on x86 manually is correct and checking that is clearly a good idea for debug kernels. I'll have to think about this a bit: assuming only vmf_insert_pfn() calls pfnmap_setup_cachemode_pfn() but vmf_insert_pfn_prot() doesn't, how could we sanity check that somebody is doing something against the will of PAT. -- Cheers David / dhildenb