From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 ADFA629292C for ; Mon, 12 May 2025 12:05:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747051552; cv=none; b=ow1xo9f60NIxYWM8frEBk4jpWUOkbWefvZpbyCWFAONldl8ZxHNKVhFuXX13z5cw60rR7q+bnPtvKpFGVFsnysWx7o30GIeGo459RKHij1/mCZRlEe36tPEB2/F/GyunAjlFj9K+hnnCqO8kR+mEEIfzJcAVQYrM/VJTQ3qFefg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747051552; c=relaxed/simple; bh=7dbu82ejJ+k5pWlX8fg5pJ+AOfvHzyYIV9fHhxpAldc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GwWTnvX6tV8BfV7FQJbGf1y9ILG+QYCUoY3GUCdNhN5YZd077zo2cyf8tLsxm6yl5EfEeXEPdhO8cmmqldcbfPTPyhBE4Cq/o58wZWhhVWLaJ+t2ls5x1xfdZKX9kYQywmdugphaZtONnne/KSJqIavNmZD9sLlfTD1X7arMYnY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=gs3PV9Hd; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="gs3PV9Hd" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747051549; 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=wdJlzktGGrJqFesVqic51nFN+xlPwzqlSYZMp8S0TxI=; b=gs3PV9HdfUEH/WxJRReWKNevdsQxZpDxRcxxA3wvi063o3GtVmp1en9tI4WEtJPcQTh599 BawGcd3IPTcVNsjuP1wLDWTmCrk70g2lEcbddVujwLtER68Iy11Y6kZ75LxUVAgR5mh7vf wX6uqRz4g+6ahy8RVGgKxE3GIeHGlP0= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-329-A75BA0A7PAiOujQc6fCJmg-1; Mon, 12 May 2025 08:05:48 -0400 X-MC-Unique: A75BA0A7PAiOujQc6fCJmg-1 X-Mimecast-MFC-AGG-ID: A75BA0A7PAiOujQc6fCJmg_1747051547 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-43cf5196c25so21564085e9.0 for ; Mon, 12 May 2025 05:05:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747051547; x=1747656347; 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=wdJlzktGGrJqFesVqic51nFN+xlPwzqlSYZMp8S0TxI=; b=f9F4KEkxAxODP5eYjIA4gF6Mo7qC9WsxvjEjS+/D6zR6J27Vzluvxki2jeHPIDu5dP heP4FVGkJCXtVCKHI7g9mioZD3LdemIVgcxmeQBkDDZFxSKyMUCwQT+Sc46RXwLFcHSa h9Bxj0UybVn7UqJoM30qfz3PQoleGmz4ar3cSDI85VxrgcFdjJCD23B3lafTVrQf8qhx Snmv/2wAj4RjvF64QvYq8CMNVjoNZqY1vnQ6J37MUOH0v/PIRn6JY+qrY2nwevJ5BmB5 Ue5OH0dyreO0HEpybeMl7GzBzY0fYI5h/vP9kmk7uIRw2NcAnHmwC/oQVlNNEIN8V/RT MvDw== X-Forwarded-Encrypted: i=1; AJvYcCXcsdkor7YNennGwTIRXERt2UA8kmiESrnjrcMLGjc4wvwe+joIeNNFxw3Rh4OguD1R8wSOBow18Bd6J+Q=@vger.kernel.org X-Gm-Message-State: AOJu0YyOxsK9ZMnj4IWnkQhYr81Nyfdczxx4JpnJ5YhEk8kQyBiSWmIc 46qjWiXKmLRmzHDAleXDZpYIHVsmXJIHGXf8ukh1r/fEbY1bJku4yXSA1MGPYcGm8C0NXAfU7aY PGlsY8fY4LekVGxg/V40MbEtUwJrQEUnji3e0EyjlHd76rNxYBfvSsYegH7b4HQ== X-Gm-Gg: ASbGncuwhcDD6RxtsLkctImHf6RdAdCoKJD1QMPDtsPJKAniRGkPM0x0roL7hTjOLzj Ilb1/8wQgqphibsRv42ovPi5Ryx6mn7L5iuSGI8DFCQwFIxrHh7DfcS9y8G6DTrtqOE0PetYJmH 7mdNQ4Rf/OvZPOo39uyeelkJAusee2ahuV9ooI2/bP53jY7lcQDmMOKh1s0IbF4886Cvd1VFypS cvInKYxxMnup+wqDOvq1mBKiDwfCkqOn1+4VL1c4+jgUDhg/7Yh1s/osuyC9noOG42A8r45qDqh Ghivq0dO+OqG/t5oi03OKGcHO0+tz8v358lke2tuJh1wWPszTbVPcLWv+6ch5FRaQBFJUW5XG2c 67PBzxmSNut6CN/rd1BVZO/PloFVzn5OG+ydpHw0= X-Received: by 2002:a05:6000:2a1:b0:3a0:b733:f262 with SMTP id ffacd0b85a97d-3a1f64ab58bmr10472091f8f.51.1747051547093; Mon, 12 May 2025 05:05:47 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFASPPotExaPDA1hbZyCJdrcf7Y8GXHdAS7ODG1uszxEfWE0IHpAxbF5G0Tk+V/yx8Uk0/lbA== X-Received: by 2002:a05:6000:2a1:b0:3a0:b733:f262 with SMTP id ffacd0b85a97d-3a1f64ab58bmr10472042f8f.51.1747051546618; Mon, 12 May 2025 05:05:46 -0700 (PDT) Received: from ?IPV6:2003:d8:2f4a:5800:f1ae:8e20:d7f4:51b0? (p200300d82f4a5800f1ae8e20d7f451b0.dip0.t-ipconnect.de. [2003:d8:2f4a:5800:f1ae:8e20:d7f4:51b0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a1f57de100sm12085800f8f.2.2025.05.12.05.05.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 May 2025 05:05:46 -0700 (PDT) Message-ID: <836f2574-cb60-44c5-865c-7f13a90779ec@redhat.com> Date: Mon, 12 May 2025 14:05:45 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/mm: Disable barrier batching in interrupt contexts To: Ryan Roberts , Catalin Marinas , Will Deacon , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , "Matthew Wilcox (Oracle)" , Mark Rutland , Anshuman Khandual , Alexandre Ghiti , Kevin Brodsky Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+5c0d9392e042f41d45c5@syzkaller.appspotmail.com References: <20250512102242.4156463-1-ryan.roberts@arm.com> <001dfd4f-27f2-407f-bd1c-21928a754342@redhat.com> 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: 8bit >>>   static inline void arch_leave_lazy_mmu_mode(void) >>>   { >>> +    if (in_interrupt()) >>> +        return; >>> + >>>       arch_flush_lazy_mmu_mode(); >>>       clear_thread_flag(TIF_LAZY_MMU); >>>   } >> >> I guess in all cases we could optimize out the in_interrupt() check on !debug >> configs. > > I think that assumes we can easily and accurately identify all configs that > cause this? We've identified 2 but I'm not confident that it's a full list. Agreed. I was wondering if we could convert the ones to use different pte helpers, whereby these helpers would not be available without CONFIG_WHATEVER. Then, make these features select CONFIG_WHATEVER. VM_WARN_ON_* would be used to catch any violations / wrong use of pte helpers. > Also, KFENCE isn't really a debug config (despite me calling it that in the > commit log) - it's supposed to be something that can be enabled in production > builds. Agreed. Even Fedora has it. > >> >> Hm, maybe there is an elegant way to catch all of these "problematic" users? > > I'm all ears if you have any suggestions? :) > > > It actaully looks like x86/XEN tries to solves this problem in a similar way: Heh, yes. Good old xen ... > > enum xen_lazy_mode xen_get_lazy_mode(void) > { > if (in_interrupt()) > return XEN_LAZY_NONE; > > return this_cpu_read(xen_lazy_mode); > } > > Although I'm not convinced it's fully robust. It also has: > > static inline void enter_lazy(enum xen_lazy_mode mode) > { > BUG_ON(this_cpu_read(xen_lazy_mode) != XEN_LAZY_NONE); > > this_cpu_write(xen_lazy_mode, mode); > } > > which is called as part of its arch_enter_lazy_mmu_mode() implementation. If a > task was already in lazy mmu mode when an interrupt comes in and causes the > nested arch_enter_lazy_mmu_mode() that we saw in this bug report, surely that > BUG_ON() should trigger? Hm, good point. But that code is old, so probably something seems to be preventing that? In any case, just a thought on the in_interrupt() check, I think this commit is good enough as is. -- Cheers, David / dhildenb