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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B3ECC4829B for ; Mon, 12 Feb 2024 13:13:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1DEA96B0074; Mon, 12 Feb 2024 08:13:14 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 167CA6B0078; Mon, 12 Feb 2024 08:13:14 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EADF76B0080; Mon, 12 Feb 2024 08:13:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id D4AB46B0074 for ; Mon, 12 Feb 2024 08:13:13 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 763521A0A29 for ; Mon, 12 Feb 2024 13:13:13 +0000 (UTC) X-FDA: 81783192666.16.00DA1EB Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf12.hostedemail.com (Postfix) with ESMTP id 5A3AD40011 for ; Mon, 12 Feb 2024 13:13:11 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=NtvMES3J; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf12.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707743591; h=from:from:sender: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:dkim-signature; bh=Hww63RycILkhWmUV7kV9IBG+ru1x1IcPxqyllH9PLOo=; b=QV93BJLsj9+hB8+ATfwGoFLVppSAygVd5Br80vLwmhJqrfuwlvcMu9uJJvKtwSyDpmr0qp JTCwzF9g6dpeSxuYLtULtLu+vGOBdeXY056zEko2ynFmDYPBAyaIcVFqCTN08kNvfysbzs WuKMGCgyNOr4vY+KbJVr5yfGzquYxFI= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=NtvMES3J; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf12.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707743591; a=rsa-sha256; cv=none; b=RQc6Xf6s8sSE3NzfFzU96p+RAViP7dw3wc301pcDzthVrcHya+hZakxYBkdP3nSZbasRnE Q2QskvJ4n1qK37mMqGDHJDKIdMLOzQAw06gzvwHijZaIOemrtQlYl/KynRKMGMFlXPN9l+ YFo6fnXLO3BABkCCPDfVamND+p0SLu8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707743590; 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=Hww63RycILkhWmUV7kV9IBG+ru1x1IcPxqyllH9PLOo=; b=NtvMES3JDRz+gOZrytBvubZ/ImWAIzdiNH4fUMRP702TYpgmvrexrdC22dVZ4EePkpEnII B5zYrhAqES7qIW9HOow66bXolaXz9xEjBlUXlM23LDYDtp13Wp3Roo0o6qmvqB2r4eq3BD u4KjjQ6K22BwgmcGrT/1gR5JCdT3rSw= 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-365-0_kmJHeZMS-6YNz5SiDb_A-1; Mon, 12 Feb 2024 08:13:09 -0500 X-MC-Unique: 0_kmJHeZMS-6YNz5SiDb_A-1 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-33b1ad7dfe1so1622649f8f.2 for ; Mon, 12 Feb 2024 05:13:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707743587; x=1708348387; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Hww63RycILkhWmUV7kV9IBG+ru1x1IcPxqyllH9PLOo=; b=QTu/iLGKVFtwf/VEo2uFWl6TztsvLCB+hB8VA6oi+XtwSLy3+EdRcqdXAXzt4hYgAv dkd+j8k6d94tnCq2+wH/kfPIaPX0fJJ2PCVrX3/sAgmS71sqQfPdfHai1cpDIdlD4SAP PRQ2GcW5BCKLxKWHwGWVdvFuoAEh21B8C5X3/R/0iWjrFWokELQfFZd5rpAFY6jeqmxU mHFe5PNFnG3saM4IYo5R0W3N2y5qgkPzp9IBqV6NID2fctyyIwF9p8/3o9h0ucZRgRbK 0tJp+ZByON+bcDQNWpLZq+DZm0JvctX8HY/Ic+/lI26biApOGky9ClkzZ2CddsSW5LLw xQ1g== X-Gm-Message-State: AOJu0YxH4BuJQSYI7OcmmXCLzgu3UEUuCNagvD2XL8B7jvTsLuu0nn0a J8Ot9TAzQJmTv98/COkvFIVUTnuujIs17uEoOBu8xcwI9lMpt0UpthC2a1eWQqaPV4jTq1e1mW8 IoPK5l14omnk++hogMUtg4o5d1XYY66NZl58n/z92m0uY6y+Z X-Received: by 2002:a5d:6486:0:b0:33b:2300:9cdc with SMTP id o6-20020a5d6486000000b0033b23009cdcmr7236127wri.46.1707743587346; Mon, 12 Feb 2024 05:13:07 -0800 (PST) X-Google-Smtp-Source: AGHT+IEReINvzzr3H3VeDrYjZvaBxMo8PW95UvCVHUhmv21+hC5vvpCm8WTG48/ufAWGbGiAoJPPvA== X-Received: by 2002:a5d:6486:0:b0:33b:2300:9cdc with SMTP id o6-20020a5d6486000000b0033b23009cdcmr7236087wri.46.1707743586951; Mon, 12 Feb 2024 05:13:06 -0800 (PST) X-Forwarded-Encrypted: i=1; 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 bGQBPpq2 4FEEQifKZjTIU02Tf7cbrbE3std9+7VYMZtSN8ow3ZMho9DSfMsFshcXi7IrBQjs3eaE6roSK1Ci0cvCQ6ZsaY50LI19L30xDdDEsJN60TWYUfLupgPQTHWE7JOryQy4zkCgzfF1srp0GLCDtV3PBfnctsJ5+KPMRBg+dlHvtAfRzm7TXFDOfiJd+Luhuksi21pxTg2vINRJheJIiGsbdMMYI9/ACXKt7i4+gB8H8st97ckVnIGfalVW/sWoJWe88CbAu5yy0wkW3eyV1EAf4W+IBe4Y6m83uKzJWFOhK4vYhveT/wkym+/0Eelze0DHYINSgRdvq8jojh Received: from ?IPV6:2003:cb:c730:2200:7229:83b1:524e:283a? (p200300cbc7302200722983b1524e283a.dip0.t-ipconnect.de. [2003:cb:c730:2200:7229:83b1:524e:283a]) by smtp.gmail.com with ESMTPSA id x8-20020a5d6508000000b0033b1b01e4fcsm6805291wru.96.2024.02.12.05.13.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Feb 2024 05:13:06 -0800 (PST) Message-ID: <165363ba-d6cc-47a7-ab2a-d3a27a42f739@redhat.com> Date: Mon, 12 Feb 2024 14:13:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 2/4] mm: introduce new flag to indicate wc safe To: ankita@nvidia.com, jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, reinette.chatre@intel.com, surenb@google.com, stefanha@redhat.com, brauner@kernel.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, alex.williamson@redhat.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, andreyknvl@gmail.com, wangjinchao@xfusion.com, gshan@redhat.com, shahuang@redhat.com, ricarkol@google.com, linux-mm@kvack.org, lpieralisi@kernel.org, rananta@google.com, ryan.roberts@arm.com, linus.walleij@linaro.org, bhe@redhat.com Cc: aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, kvmarm@lists.linux.dev, mochs@nvidia.com, zhiw@nvidia.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20240211174705.31992-1-ankita@nvidia.com> <20240211174705.31992-3-ankita@nvidia.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 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: <20240211174705.31992-3-ankita@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 5A3AD40011 X-Stat-Signature: 8njuxw4hkf6a8pn4o1npk1a3jzsh3hee X-HE-Tag: 1707743591-51796 X-HE-Meta: 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 z+4BLyoS wMC70wm/xi7f2+XnfmsJscPJ3PCNM0js+iNBLkzU85r412trZA3H+cwW+FziID7PFad1h3BxeXPdOZACjtMy39yj2oaS0iggF3cpA+uIhlUtuBo/2um1Qg0/GmWRaPGT6hhrylt6xmW5Apc+jaiLQ1qh8g/x9TK+ZovgiHSfdtUlzWHA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11.02.24 18:47, ankita@nvidia.com wrote: > From: Ankit Agrawal > > Generalizing S2 setting from DEVICE_nGnRE to NormalNc for non PCI > devices may be problematic. E.g. GICv2 vCPU interface, which is > effectively a shared peripheral, can allow a guest to affect another > guest's interrupt distribution. The issue may be solved by limiting > the relaxation to mappings that have a user VMA. Still there is > insufficient information and uncertainity in the behavior of s/uncertainity/uncertainty/ > non PCI drivers. > > Add a new flag VM_ALLOW_ANY_UNCACHED to indicate KVM that the device > is WC capable and these S2 changes can be extended to it. KVM can use > this flag to activate the code. > MM people will stumble only over this commit at some point, looking for details. It might make sense to add a bit more details on the underlying problem (user space tables vs. stage-1 vs. stage-2) and why we want to have a different mapping in user space compared to stage-1. Then, describe that the VMA flag was found to be the simplest and cleanest way to communicate this information from VFIO to KVM. > Suggested-by: Catalin Marinas > Reviewed-by: Jason Gunthorpe > Signed-off-by: Ankit Agrawal > --- > include/linux/mm.h | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f5a97dec5169..59576e56c58b 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -391,6 +391,20 @@ extern unsigned int kobjsize(const void *objp); > # define VM_UFFD_MINOR VM_NONE > #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ > > +/* > + * This flag is used to connect VFIO to arch specific KVM code. It > + * indicates that the memory under this VMA is safe for use with any > + * non-cachable memory type inside KVM. Some VFIO devices, on some > + * platforms, are thought to be unsafe and can cause machine crashes > + * if KVM does not lock down the memory type. > + */ > +#ifdef CONFIG_64BIT > +#define VM_ALLOW_ANY_UNCACHED_BIT 39 > +#define VM_ALLOW_ANY_UNCACHED BIT(VM_ALLOW_ANY_UNCACHED_BIT) > +#else > +#define VM_ALLOW_ANY_UNCACHED VM_NONE > +#endif > + > /* Bits set in the VMA until the stack is in its final location */ > #define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ | VM_STACK_EARLY) > It's not perfect (very VFIO <-> KVM specific right now, VMA flags feel a bit wrong), but it certainly easier and cleaner than any alternatives I could think of. Acked-by: David Hildenbrand -- Cheers, David / dhildenb