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 C2754C7EE26 for ; Fri, 19 May 2023 18:25:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 25434900004; Fri, 19 May 2023 14:25:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 203FF900003; Fri, 19 May 2023 14:25:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F294900004; Fri, 19 May 2023 14:25:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 00A6C900003 for ; Fri, 19 May 2023 14:25:58 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 252A040B27 for ; Fri, 19 May 2023 18:25:58 +0000 (UTC) X-FDA: 80807833596.08.D6F75F4 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) by imf07.hostedemail.com (Postfix) with ESMTP id 669FC40010 for ; Fri, 19 May 2023 18:25:56 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=EHWVv93H; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf07.hostedemail.com: domain of 3M79nZAYKCHoqcYlhaemmejc.amkjglsv-kkitYai.mpe@flex--seanjc.bounces.google.com designates 209.85.219.201 as permitted sender) smtp.mailfrom=3M79nZAYKCHoqcYlhaemmejc.amkjglsv-kkitYai.mpe@flex--seanjc.bounces.google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1684520756; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UkvqDfyMOLrjy8YMY1wwRgMIQfqQZGbB8xX3NIFQuJ8=; b=llqwX7HLfguU1BmeTft7YWxtl26A37Ua5q7Gp7nDIrC9BA0DAyG2ErJoT3dvdhYs7rro/c YGIlnZ4fstSaMPsCpGViINmWKDMufBKTMiNokxWzCEhgfRJKMZzThtcTqT03qxPsqnDSC+ x5PsaPvRKtqdqw0+04gX7FbNyIwkePs= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=EHWVv93H; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf07.hostedemail.com: domain of 3M79nZAYKCHoqcYlhaemmejc.amkjglsv-kkitYai.mpe@flex--seanjc.bounces.google.com designates 209.85.219.201 as permitted sender) smtp.mailfrom=3M79nZAYKCHoqcYlhaemmejc.amkjglsv-kkitYai.mpe@flex--seanjc.bounces.google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1684520756; a=rsa-sha256; cv=none; b=3O6PqYR/h/qMqnEXHvrXyXx805jujXWg8mX5lb+BWRXHeo5Lj+LOMwbNEyjgJMuFGT2j1p JaPIyjFrRZkCyk7GlJsVlDIEcV5Cn4nHZP8nnu7OE/oKv88RKt0MpaT6GHhbth+RgbeIAz gPgjOM0A76ttl2KWk7NDrnW/bQgsSo8= Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-ba9d8b01f82so1611009276.0 for ; Fri, 19 May 2023 11:25:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1684520755; x=1687112755; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=UkvqDfyMOLrjy8YMY1wwRgMIQfqQZGbB8xX3NIFQuJ8=; b=EHWVv93HNkwFD6Rzv38Ipc2B9rPBD1UDSNb25aEyGm9tgrL4HAfKR3FhP4mF0gDZ8o 5akGYCEZHakPY7q+34PKZr+wjUxJKbOWkHSdmCIF9EthXaS0GE1aeTDaAYg74+n8LxZv NrNY0cT19gsI9F6xDoZFfVqJL3/PXEZm7iHMz8EEbdrZb3BVlRolZpZs2icBr5OUNum5 NS6M57Pod3yr/sG/iNpxrle6ypJpM2UH+leYpSYYesmxJnETM/FgFp+u2mEeUpZlkVpR gVvuRxOcV30/Oziq9eKB/d6UWnrG6nSzoKyR8Y2BOsFA/g06gQPoCPP9LQW1NpKMIWBr bE6g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684520755; x=1687112755; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UkvqDfyMOLrjy8YMY1wwRgMIQfqQZGbB8xX3NIFQuJ8=; b=U71BKW00feAZhsd5zgJBHzyWTMsvXE/LsidyAaB4g/yKxopVkr2Wjvki4Ric1aXVBX gHudp07gsnt0FyvHNSORGGS1eGXzFFvXpe8X7zdwSnFssEJs7VhZpWaoyKbOE/BbqKBe baXSYKgJxX0kbOqzL2X0VmfOZPIZ8tZ/5AmCFtKTMj8YbC5kBlz+iHMJsDY+bxYCAHVH 83oZ62onlJ+CVmyeCounnYaadeWq48gngznjxPpJ7HMfTmoKOJShUaEiy1QMInok/JS4 C6iWeUX2/83cLKW4ujKJN4B96PJ55hY4xP8mvF4wkCOMM348fUEOUngeLwdGptQlk4VF UOJw== X-Gm-Message-State: AC+VfDwXl1aVQoLL3RSUSwrrBwycrtNMF6Lbah70DADX08CAnR/5gr62 a4AXU6KskZu9RRzVXTrRlVzhJ1NnCQ0= X-Google-Smtp-Source: ACHHUZ78HIA/K1sflsbUYSUjC6gecUrhcvhYYTntQ6SB2UFg6TeL234xl9KHrlPWo8SNMaksMPK95sULPeI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:8402:0:b0:ba8:797c:9bc7 with SMTP id u2-20020a258402000000b00ba8797c9bc7mr1655166ybk.11.1684520755427; Fri, 19 May 2023 11:25:55 -0700 (PDT) Date: Fri, 19 May 2023 11:25:53 -0700 In-Reply-To: <20230519162432.GG4967@kernel.org> Mime-Version: 1.0 References: <20230308094106.227365-1-rppt@kernel.org> <20230519162432.GG4967@kernel.org> Message-ID: Subject: Re: [RFC PATCH 0/5] Prototype for direct map awareness in page allocator From: Sean Christopherson To: Mike Rapoport Cc: Rick P Edgecombe , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "peterz@infradead.org" , "tglx@linutronix.de" , "song@kernel.org" , "dave.hansen@linux.intel.com" , "vbabka@suse.cz" , "x86@kernel.org" , "akpm@linux-foundation.org" Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 669FC40010 X-Stat-Signature: 6s5f31u7fgu6siu5xpi7k5wrcikwrc4q X-HE-Tag: 1684520756-60360 X-HE-Meta: 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 00mBI2Oe 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 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: On Fri, May 19, 2023, Mike Rapoport wrote: > On Fri, May 19, 2023 at 08:40:48AM -0700, Sean Christopherson wrote: > > On Thu, Mar 09, 2023, Mike Rapoport wrote: > > > On Thu, Mar 09, 2023 at 01:59:00AM +0000, Edgecombe, Rick P wrote: > > > > On Wed, 2023-03-08 at 11:41 +0200, Mike Rapoport wrote: > > > > > From: "Mike Rapoport (IBM)" > > > > > > > > > > Hi, > > > > > > > > > > This is a third attempt to make page allocator aware of the direct > > > > > map > > > > > layout and allow grouping of the pages that must be unmapped from > > > > > the direct map. > > > > > > > > > > This a new implementation of __GFP_UNMAPPED, kinda a follow up for > > > > > this set: > > > > > > > > > > https://lore.kernel.org/all/20220127085608.306306-1-rppt@kernel.org > > > > > > > > > > but instead of using a migrate type to cache the unmapped pages, the > > > > > current implementation adds a dedicated cache to serve __GFP_UNMAPPED > > > > > allocations. > > > > > > > > It seems a downside to having a page allocator outside of _the_ page > > > > allocator is you don't get all of the features that are baked in there. > > > > For example does secretmem care about numa? I guess in this > > > > implementation there is just one big cache for all nodes. > > > > > > > > Probably most users would want __GFP_ZERO. Would secretmem care about > > > > __GFP_ACCOUNT? > > > > > > The intention was that the pages in cache are always zeroed, so __GFP_ZERO > > > is always implicitly there, at least should have been. > > > > Would it be possible to drop that assumption/requirement, i.e. allow allocation of > > __GFP_UNMAPPED without __GFP_ZERO? At a glance, __GFP_UNMAPPED looks like it would > > be a great fit for backing guest memory, in particular for confidential VMs. And > > for some flavors of CoCo, i.e. TDX, the trusted intermediary is responsible for > > zeroing/initializing guest memory as the untrusted host (kernel/KVM) doesn't have > > access to the guest's encryption key. In other words, zeroing in the kernel would > > be unnecessary work. > > Making and unmapped allocation without __GFP_ZERO shouldn't be a problem. > > However, using a gfp flag and hooking up into the free path in page > allocator have issues and preferably should be avoided. > > Will something like unmapped_alloc() and unmapped_free() work for your > usecase? Yep, I'm leaning more and more towards having KVM implement its own ioctl() for managing this type of memory. Wiring that up to use dedicated APIs should be no problem. Thanks!