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 AD7A1C4345F for ; Thu, 11 Apr 2024 18:48:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CC5576B0082; Thu, 11 Apr 2024 14:48:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C758A6B0085; Thu, 11 Apr 2024 14:48:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B16506B0087; Thu, 11 Apr 2024 14:48:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 8EF196B0082 for ; Thu, 11 Apr 2024 14:48:05 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0E18A1A07F3 for ; Thu, 11 Apr 2024 18:48:05 +0000 (UTC) X-FDA: 81998135730.14.22FDB1E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf06.hostedemail.com (Postfix) with ESMTP id DEFD818000D for ; Thu, 11 Apr 2024 18:48:02 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=imMqXDly; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf06.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1712861282; a=rsa-sha256; cv=none; b=Ku+gXJf73m+V6zs/HgubHGNmsbyL+DWURGmcEoYU8oPZqUwSriGMb02pj8jb3xl6EtzBLx DWTOzaOSb7CTihuo41mDK9wOG9b7CN9HhsZcma4E07uesG65JmqaP6D7SIbWRpaCRHWPWJ 0b4JNMFnVJrUM8JSyVgnn5CCCsbdWLU= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=imMqXDly; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf06.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1712861282; 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=KZYsCvW//u/CQQXOA7VquWR1RJVn5i/6cYVGpW0idNY=; b=x7sfbnhTH1UBUHGAf9izE+Jg/8AGzMyiygC3HQCXZ5BKcFZiFoWVVDx4ovzMZwZdslo7s2 5+cpUnvrQt8Ry6tOWTK+cUt3fvKlAHbZ3ShmXn/rsQQzRUy5+iPbulC+v2IWmU1NM3oIK2 oXUlwOnmQPUcEmhTmxs1qqaOk+E/Mj8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712861282; 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; bh=KZYsCvW//u/CQQXOA7VquWR1RJVn5i/6cYVGpW0idNY=; b=imMqXDlyYRB3gASRX7MzCg2dE5VCfCb3OpbDsrjxtY6cIb/uw9+y3HiKQ5YQqCyD2oX5/1 vAw8UKke3EXmDQXiW/G5/dj8WLnBoyFPEwW1vevz900eSgZSN3aP/izEvxGx6JbHuyvLlO +lF1ize9TRw+1dYEl+MIu5zqu+24ylk= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-652-nX5eyaAHN7-UIOtjt9Awgw-1; Thu, 11 Apr 2024 14:48:00 -0400 X-MC-Unique: nX5eyaAHN7-UIOtjt9Awgw-1 Received: by mail-qv1-f71.google.com with SMTP id 6a1803df08f44-69a01201ca0so696906d6.0 for ; Thu, 11 Apr 2024 11:48:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712861280; x=1713466080; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=KZYsCvW//u/CQQXOA7VquWR1RJVn5i/6cYVGpW0idNY=; b=IRr8e4HO3rxvKxV9FWKZUQIvQe+c1qR5QjS8zuiR1TMilM5SgM4CFOBOafDQ08VwN8 YzntAIZfZAjscPnqqzyxM4T/biTdygiSCgl41Taj27qbxvEH5DDdtOZ1a0/9wlqhyhIN 8C7FjFapNwyPc1BgiGMYJ1NAHMu4saotogQWAwn/yM67Ug3sylR5PIdAaTI3BBUl7vfE mdXr/2Sg/KKATI3zR9hvLcMnIsPAuzbxIh9QXleRaUTgrhZZRkCZI0NxAkWkVWJ6LxOE ZJftvVinCL/zBRyS0DUDKDnRSnILoEJddDfrg6ZdgCHOo/MMmVpQFdckrP97XaetjvFu hQyw== X-Forwarded-Encrypted: i=1; AJvYcCXCR/prz/NTibY4ZwF/xvnU8mCdioQRZ95Tgt6t/KcUWKCr7LdQU7dl0VoHjLgrQvjFJybKW5efNxF0fsuogXIJ4Go= X-Gm-Message-State: AOJu0YwThRoB+TGG72b09iCUB78CwdYcFcRMvj4MVNIypQe0WtU2COSK NiGPrKGAWTM+6wTGFTtjilpOOTa7FqnSGknYKAb3uT1xFTQuK1MdVcY2XTFm7KGxRgYYjbUIWfV XDKcQGDqOhaGk/CZROxY7zP2HuQUDjUWaroVfl4VGmKHON7Aj X-Received: by 2002:a05:6214:5299:b0:69b:1c5c:28fb with SMTP id kj25-20020a056214529900b0069b1c5c28fbmr648143qvb.0.1712861279778; Thu, 11 Apr 2024 11:47:59 -0700 (PDT) X-Google-Smtp-Source: AGHT+IE7S/NCpZfvRlaXUMSJjHCJMO0BUAFkMZwp6uvumqLHKeYZXzRRk2gozszNqWEk8Im7F5OglA== X-Received: by 2002:a05:6214:5299:b0:69b:1c5c:28fb with SMTP id kj25-20020a056214529900b0069b1c5c28fbmr648100qvb.0.1712861279132; Thu, 11 Apr 2024 11:47:59 -0700 (PDT) Received: from x1n (pool-99-254-121-117.cpe.net.cable.rogers.com. [99.254.121.117]) by smtp.gmail.com with ESMTPSA id ej6-20020ad45a46000000b00696b1050be8sm1276159qvb.133.2024.04.11.11.47.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Apr 2024 11:47:58 -0700 (PDT) Date: Thu, 11 Apr 2024 14:47:56 -0400 From: Peter Xu To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Thomas Bogendoerfer , Nicholas Piggin , Anup Patel , Atish Patra , Sean Christopherson , Andrew Morton , David Hildenbrand , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Andrea Arcangeli Subject: Re: [PATCH 1/4] KVM: delete .change_pte MMU notifier callback Message-ID: References: <20240405115815.3226315-1-pbonzini@redhat.com> <20240405115815.3226315-2-pbonzini@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: DEFD818000D X-Stat-Signature: m81jqt3k8donttr9x96kjpsaczxkqb9t X-HE-Tag: 1712861282-662730 X-HE-Meta: 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 PHAmY8Gf 0Fk1Tsrj5NKiDp4xdlvp2GGdQQ9j1d8gaJKzqINrKRVLKJgDId+IbgfjtOutNx5tzgI0lY8QQIZvol4rY7tSUld/iO+TvKpwe5YEcliHana62AvFzS8COy+F4DeR25MV8hkIGggWExEbc+Akc6eCnauoa8mua5R2v6c8ftfIZrgHKOO9fJIGWfLmlKGwRMyESMSunL/cKkhz5AFgzinSLYgO7hiMj8GLDOQDUpD9LU77vO8SU5uveJo1FuRY8GZ0XM1HqUzBhaDPiAqKNU35dDs4AqkmVmhQDqZRCuPgIqLiSuu2z49NKO0NuhwgLoxH9nfjZ7zk4/a2GeI4W+i/jQvmvElFk7+HKsaEXdlUCA9qbG2JhZja9/XMgP8NCvG1MR4H+6ZUKOANWyrlFatcR0/sW1Gw16iX2UZI7CXXoyuZpm2aznq+W6flARF7Pe+5KhPVoykefy6/j0y4sGQgMXbZ81jHh1S12+SIR X-Bogosity: Ham, tests=bogofilter, spamicity=0.011243, 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 Thu, Apr 11, 2024 at 06:55:44PM +0200, 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 > has ever reported an issue for over 10 years, so I think it's easiest > to just rip the code out. Right, it was pretty old and I have no idea if that was discussed or published before.. It would be better to have discussed this earlier. As long as we have a decision with that being aware and in mind, then it looks fine to me to take either way to go, and I also agree either way is better than keep the status quo. I also have Andrea copied anyway when I replied, so I guess he should be aware of this and he can chim in anytime. Thanks! -- Peter Xu