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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 D4B2BC4345F for ; Fri, 12 Apr 2024 20:02:02 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Td4UcS6p; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Td4UcS6p; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4VGSBx1xJnz3vbY for ; Sat, 13 Apr 2024 06:02:01 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Td4UcS6p; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Td4UcS6p; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=david@redhat.com; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4VGSB51Nplz3dX4 for ; Sat, 13 Apr 2024 06:01:16 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712952072; 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=cJXZRHmv8/e3DunpfzJ0mbDtlVWEoORc9ryXYI3O8bI=; b=Td4UcS6pPK0cHtOfclS0Qn/xkgwRtCWK8OUljfLe1DnrZqXc6h2aSGO8jIX6EMEXQwhxpi 7yKFVGjVYjb+ivahZMyIkepn7LnIUTVVxGUZcJdBbnqEEMuyLZI7IrvwIfAmfyHIQfy+TJ 3QB4JY1jP1wdvkoT74f/Zzf8RZ/UBB4= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712952072; 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=cJXZRHmv8/e3DunpfzJ0mbDtlVWEoORc9ryXYI3O8bI=; b=Td4UcS6pPK0cHtOfclS0Qn/xkgwRtCWK8OUljfLe1DnrZqXc6h2aSGO8jIX6EMEXQwhxpi 7yKFVGjVYjb+ivahZMyIkepn7LnIUTVVxGUZcJdBbnqEEMuyLZI7IrvwIfAmfyHIQfy+TJ 3QB4JY1jP1wdvkoT74f/Zzf8RZ/UBB4= Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-323-z9MOQQJvPhONCxLzIx-OfQ-1; Fri, 12 Apr 2024 16:01:08 -0400 X-MC-Unique: z9MOQQJvPhONCxLzIx-OfQ-1 Received: by mail-lj1-f199.google.com with SMTP id 38308e7fff4ca-2d883dab079so10987141fa.3 for ; Fri, 12 Apr 2024 13:01:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712952066; x=1713556866; 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=cJXZRHmv8/e3DunpfzJ0mbDtlVWEoORc9ryXYI3O8bI=; b=Hq0m+QyrV+qwrV2Xf+V/OdF5NwzQ6wxylf4JKvVGbKmlD+sxOwzx5PxFo0+XVLMCeX UH8yb5M7k2J3xdXzSn31CUHiKG8Jo/YLq00ReIJ2mbhDKcdQF84JblNXovYNFI8V5R3h KFcaByfKm/+cBqJsi9bU/A0rfNAyXHm2H1+VZbsGoosXKPtrt0vk4cay15SkxvfcsM81 dlfLtzsZy83PwZHO2EmaJoh4NnMH+6RShFlcwaopQhix50206ZGnWt9CL/1WfRgkRR9u zycv1VRSvEePuedUVYC/1u6R8UHydLG2p1rAtgV97lL0b+YSym++FgoYOEslsl41f81p JAUQ== X-Forwarded-Encrypted: i=1; AJvYcCVprISU5mndghrD7guSGVl+CuXDmwgx20lnPAxx9DO/cGEuVQfgAazXapXWpEUQZkD0X4clcLxM/xapq0e0zOzI9iwazRfa5DqQ2jz4iQ== X-Gm-Message-State: AOJu0YwVqfVaYAvU32S73BZxTA1OX2KDG3Oho37EfoGLc0JCc+aBlthh YuwLktEnrhci/WV7NZA+uRtxc9DMwLCUz4M2FzPfYgZxFX/I5Fu/Z8Rhma7QDve3Zh6B7GJINa4 fgHX2H9drdBElG9X1M78fy3/zRz7Zc8NjIybmAndbMOn9Bw3Ad2LaqZw9bMdZ7Eo= X-Received: by 2002:a05:651c:2cf:b0:2d5:9bd4:4496 with SMTP id f15-20020a05651c02cf00b002d59bd44496mr2381538ljo.50.1712952066568; Fri, 12 Apr 2024 13:01:06 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH+1ZB86kc7lYTUaIgqoDegakDKAMCQ9kCvSW+1ih93sMlVewc37u5oJ4uI/kb1uzma3RPSWA== X-Received: by 2002:a05:651c:2cf:b0:2d5:9bd4:4496 with SMTP id f15-20020a05651c02cf00b002d59bd44496mr2381503ljo.50.1712952066094; Fri, 12 Apr 2024 13:01:06 -0700 (PDT) Received: from ?IPV6:2003:cb:c730:f600:afa2:4e8a:448a:9831? (p200300cbc730f600afa24e8a448a9831.dip0.t-ipconnect.de. [2003:cb:c730:f600:afa2:4e8a:448a:9831]) by smtp.gmail.com with ESMTPSA id m38-20020a05600c3b2600b00417fdf4677asm2977868wms.14.2024.04.12.13.01.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Apr 2024 13:01:05 -0700 (PDT) Message-ID: <5ed763c2-7e01-4c31-923c-ba62f0d0e993@redhat.com> Date: Fri, 12 Apr 2024 22:01:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] KVM: delete .change_pte MMU notifier callback To: Paolo Bonzini , Peter Xu References: <20240405115815.3226315-1-pbonzini@redhat.com> <20240405115815.3226315-2-pbonzini@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 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: 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: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , Marc Zyngier , linux-trace-kernel@vger.kernel.org, Nicholas Piggin , Bibo Mao , loongarch@lists.linux.dev, Atish Patra , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Thomas Bogendoerfer , Sean Christopherson , linux-kernel@vger.kernel.org, Oliver Upton , linux-perf-users@vger.kernel.org, kvm-riscv@lists.infradead.org, Anup Patel , Andrew Morton , Tianrui Zhao , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11.04.24 18:55, Paolo Bonzini wrote: > On Mon, Apr 8, 2024 at 3:56 PM Peter Xu wrote: >> Paolo, >> >> I may miss a bunch of details here (as I still remember some change_pte >> patches previously on the list..), however not sure whether we considered >> enable it? Asked because I remember Andrea used to have a custom tree >> maintaining that part: >> >> https://github.com/aagit/aa/commit/c761078df7a77d13ddfaeebe56a0f4bc128b1968 > > The patch enables it only for KSM, so it would still require a bunch > of cleanups, for example I also would still use set_pte_at() in all > the places that are not KSM. This would at least fix the issue with > the poor documentation of where to use set_pte_at_notify() vs > set_pte_at(). > > With regard to the implementation, I like the idea of disabling the > invalidation on the MMU notifier side, but I would rather have > MMU_NOTIFIER_CHANGE_PTE as a separate field in the range instead of > overloading the event field. > >> Maybe it can't be enabled for some reason that I overlooked in the current >> tree, or we just decided to not to? > > I have just learnt about the patch, nobody had ever mentioned it even > though it's almost 2 years old... It's a lot of code though and no one I assume Andrea used it on his tree where he also has a version of "randprotect" (even included in that commit subject) to mitigate a KSM security issue that was reported by some security researchers [1] a while ago. From what I recall, the industry did not end up caring about that security issue that much. IIUC, with "randprotect" we get a lot more R/O protection even when not de-duplicating a page -- thus the name. Likely, the reporter mentioned in the commit is a researcher that played with Andreas fix for the security issue. But I'm just speculating at this point :) > has ever reported an issue for over 10 years, so I think it's easiest > to just rip the code out. Yes. Can always be readded in a possibly cleaner fashion (like you note above), when deemed necessary and we are willing to support it. [1] https://gruss.cc/files/remote_dedup.pdf -- Cheers, David / dhildenb