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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B4295C982C4 for ; Fri, 16 Jan 2026 15:00:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D83596B00A3; Fri, 16 Jan 2026 10:00:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D30766B00A5; Fri, 16 Jan 2026 10:00:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C33206B00A8; Fri, 16 Jan 2026 10:00:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id B15AA6B00A3 for ; Fri, 16 Jan 2026 10:00:57 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 667F31AB20 for ; Fri, 16 Jan 2026 15:00:57 +0000 (UTC) X-FDA: 84338139354.30.E5FDCDA Received: from fra-out-015.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-015.esa.eu-central-1.outbound.mail-perimeter.amazon.com [18.158.153.154]) by imf12.hostedemail.com (Postfix) with ESMTP id E40BE40007 for ; Fri, 16 Jan 2026 15:00:54 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=amazon.com header.s=amazoncorp2 header.b=MScVtAYR; spf=pass (imf12.hostedemail.com: domain of "prvs=469074ca4=kalyazin@amazon.co.uk" designates 18.158.153.154 as permitted sender) smtp.mailfrom="prvs=469074ca4=kalyazin@amazon.co.uk"; dmarc=pass (policy=quarantine) header.from=amazon.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1768575655; h=from:from:sender:reply-to: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=ESFkuLZPGT8fbXcE99iW3+H6+Z58GdtIZgdRAPcl1wM=; b=cihTYeN8cXgWMlc1HCCSruIGmF33iqW9MAwKR3+fGiPTl4R52mABVYaZdooRtkUyYGWziO FrrJkWspHPmXtSCpf/7ZIshaqqy5z8EbEahP71Gvl5O91RvOfHLgGjYAnWZOBGxCvgcOw4 hsaIElheil/9AAmVCrM24dCcdEE/CPk= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=amazon.com header.s=amazoncorp2 header.b=MScVtAYR; spf=pass (imf12.hostedemail.com: domain of "prvs=469074ca4=kalyazin@amazon.co.uk" designates 18.158.153.154 as permitted sender) smtp.mailfrom="prvs=469074ca4=kalyazin@amazon.co.uk"; dmarc=pass (policy=quarantine) header.from=amazon.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768575655; a=rsa-sha256; cv=none; b=u8C/p/iyDTVzIRrA/rA8TVhzix5d99z0juHGZav94dzf+lYoYTA3mCE63/JbNIugLLkYRD pPefhCk+1bZxMkp+mnegaa7IWOwTDo1kRfhMN856ItDgAYxli/6c78s43+Y3gbYUZHlxfZ aqds50/ZNZeZysZ1dpc+3Of5Vakgi04= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1768575655; x=1800111655; h=message-id:date:mime-version:reply-to:subject:to:cc: references:from:in-reply-to:content-transfer-encoding; bh=ESFkuLZPGT8fbXcE99iW3+H6+Z58GdtIZgdRAPcl1wM=; b=MScVtAYRZQy6jgfplK20tVbMgmqSg72YJSpTRV/lBlnl4rgopT4cpgI4 oxc4KNbGaxHf+eQFhE8yGCVpdbFv8zantwBjJ8gtZx6Uham7vL0ZqQyK/ Bw3CAo6+FMX7vt/XKilthvVnBC39LmppZwo1buUu/dWALjotyOnJjSLLR Z7MbSFNj2BJPJJrRgOQCMGbGpZD1G0PLaKvHpi/mc0ACELQ3U6W3qSWc6 I3JDrwe01H6N/A0w6Wlh1kfEwNwFE7JA1fp4gUyJmFk1BSkdhgjCB6iYg uRbca2FweXWMK/laz1DGWrApM69bznIRRVddqKWTwNqBG2dUY8YFKdlx3 g==; X-CSE-ConnectionGUID: gk1Li/PmQKCcG3NIHCLDrw== X-CSE-MsgGUID: 3iwqWVkQSaGSUUqmLqKkqA== X-IronPort-AV: E=Sophos;i="6.21,231,1763424000"; d="scan'208";a="7898391" Received: from ip-10-6-11-83.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.11.83]) by internal-fra-out-015.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jan 2026 15:00:37 +0000 Received: from EX19MTAEUA001.ant.amazon.com [54.240.197.233:10054] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.8.163:2525] with esmtp (Farcaster) id c5194cd9-a815-4ca7-beb1-df7b75e8b434; Fri, 16 Jan 2026 15:00:37 +0000 (UTC) X-Farcaster-Flow-ID: c5194cd9-a815-4ca7-beb1-df7b75e8b434 Received: from EX19D005EUB003.ant.amazon.com (10.252.51.31) by EX19MTAEUA001.ant.amazon.com (10.252.50.223) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Fri, 16 Jan 2026 15:00:31 +0000 Received: from [192.168.12.13] (10.106.82.9) by EX19D005EUB003.ant.amazon.com (10.252.51.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Fri, 16 Jan 2026 15:00:27 +0000 Message-ID: <294bca75-2f3e-46db-bb24-7c471a779cc1@amazon.com> Date: Fri, 16 Jan 2026 15:00:26 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Subject: Re: [PATCH v9 07/13] KVM: guest_memfd: Add flag to remove from direct map To: "Edgecombe, Rick P" , "linux-riscv@lists.infradead.org" , "kalyazin@amazon.co.uk" , "kernel@xen0n.name" , "linux-kselftest@vger.kernel.org" , "linux-mm@kvack.org" , "linux-fsdevel@vger.kernel.org" , "linux-s390@vger.kernel.org" , "kvmarm@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvm@vger.kernel.org" , "bpf@vger.kernel.org" , "linux-doc@vger.kernel.org" , "loongarch@lists.linux.dev" CC: "david@kernel.org" , "palmer@dabbelt.com" , "catalin.marinas@arm.com" , "svens@linux.ibm.com" , "jgross@suse.com" , "surenb@google.com" , "riel@surriel.com" , "pfalcato@suse.de" , "peterx@redhat.com" , "x86@kernel.org" , "rppt@kernel.org" , "thuth@redhat.com" , "maz@kernel.org" , "dave.hansen@linux.intel.com" , "ast@kernel.org" , "vbabka@suse.cz" , "Annapurve, Vishal" , "borntraeger@linux.ibm.com" , "alex@ghiti.fr" , "pjw@kernel.org" , "tglx@linutronix.de" , "willy@infradead.org" , "hca@linux.ibm.com" , "wyihan@google.com" , "ryan.roberts@arm.com" , "jolsa@kernel.org" , "yang@os.amperecomputing.com" , "jmattson@google.com" , "luto@kernel.org" , "aneesh.kumar@kernel.org" , "haoluo@google.com" , "patrick.roy@linux.dev" , "akpm@linux-foundation.org" , "coxu@redhat.com" , "mhocko@suse.com" , "mlevitsk@redhat.com" , "jgg@ziepe.ca" , "hpa@zytor.com" , "song@kernel.org" , "oupton@kernel.org" , "peterz@infradead.org" , "maobibo@loongson.cn" , "lorenzo.stoakes@oracle.com" , "Liam.Howlett@oracle.com" , "jthoughton@google.com" , "martin.lau@linux.dev" , "jhubbard@nvidia.com" , "Yu, Yu-cheng" , "Jonathan.Cameron@huawei.com" , "eddyz87@gmail.com" , "yonghong.song@linux.dev" , "chenhuacai@kernel.org" , "shuah@kernel.org" , "prsampat@amd.com" , "kevin.brodsky@arm.com" , "shijie@os.amperecomputing.com" , "suzuki.poulose@arm.com" , "itazur@amazon.co.uk" , "pbonzini@redhat.com" , "yuzenghui@huawei.com" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "jackabt@amazon.co.uk" , "daniel@iogearbox.net" , "agordeev@linux.ibm.com" , "andrii@kernel.org" , "mingo@redhat.com" , "aou@eecs.berkeley.edu" , "joey.gouly@arm.com" , "derekmn@amazon.com" , "xmarcalx@amazon.co.uk" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "jackmanb@google.com" , "bp@alien8.de" , "corbet@lwn.net" , "ackerleytng@google.com" , "jannh@google.com" , "john.fastabend@gmail.com" , "kas@kernel.org" , "will@kernel.org" , "seanjc@google.com" References: <20260114134510.1835-1-kalyazin@amazon.com> <20260114134510.1835-8-kalyazin@amazon.com> Content-Language: en-US From: Nikita Kalyazin Autocrypt: addr=kalyazin@amazon.com; keydata= xjMEY+ZIvRYJKwYBBAHaRw8BAQdA9FwYskD/5BFmiiTgktstviS9svHeszG2JfIkUqjxf+/N JU5pa2l0YSBLYWx5YXppbiA8a2FseWF6aW5AYW1hem9uLmNvbT7CjwQTFggANxYhBGhhGDEy BjLQwD9FsK+SyiCpmmTzBQJnrNfABQkFps9DAhsDBAsJCAcFFQgJCgsFFgIDAQAACgkQr5LK IKmaZPOpfgD/exazh4C2Z8fNEz54YLJ6tuFEgQrVQPX6nQ/PfQi2+dwBAMGTpZcj9Z9NvSe1 CmmKYnYjhzGxzjBs8itSUvWIcMsFzjgEY+ZIvRIKKwYBBAGXVQEFAQEHQCqd7/nb2tb36vZt ubg1iBLCSDctMlKHsQTp7wCnEc4RAwEIB8J+BBgWCAAmFiEEaGEYMTIGMtDAP0Wwr5LKIKma ZPMFAmes18AFCQWmz0MCGwwACgkQr5LKIKmaZPNTlQEA+q+rGFn7273rOAg+rxPty0M8lJbT i2kGo8RmPPLu650A/1kWgz1AnenQUYzTAFnZrKSsXAw5WoHaDLBz9kiO5pAK In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.106.82.9] X-ClientProxiedBy: EX19D002EUC004.ant.amazon.com (10.252.51.230) To EX19D005EUB003.ant.amazon.com (10.252.51.31) X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E40BE40007 X-Stat-Signature: spx5muakseape8ekq4zixdei9axrtsux X-HE-Tag: 1768575654-175440 X-HE-Meta: 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 fY53o4xS 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 Ag+XX/4j xk0NUowgbphwwoOdLEKjffcurbIJu0s4yjlK6PnnaUA= 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 16/01/2026 00:00, Edgecombe, Rick P wrote: > On Wed, 2026-01-14 at 13:46 +0000, Kalyazin, Nikita wrote: >> +static void kvm_gmem_folio_restore_direct_map(struct folio *folio) >> +{ >> + /* >> + * Direct map restoration cannot fail, as the only error condition >> + * for direct map manipulation is failure to allocate page tables >> + * when splitting huge pages, but this split would have already >> + * happened in folio_zap_direct_map() in kvm_gmem_folio_zap_direct_map(). >> + * Thus folio_restore_direct_map() here only updates prot bits. >> + */ >> + if (kvm_gmem_folio_no_direct_map(folio)) { >> + WARN_ON_ONCE(folio_restore_direct_map(folio)); >> + folio->private = (void *)((u64)folio->private & ~KVM_GMEM_FOLIO_NO_DIRECT_MAP); >> + } >> +} >> + > > Does this assume the folio would not have been split after it was zapped? As in, > if it was zapped at 2MB granularity (no 4KB direct map split required) but then > restored at 4KB (split required)? Or it gets merged somehow before this? AFAIK it can't be zapped at 2MB granularity as the zapping code will inevitably cause splitting because guest_memfd faults occur at the base page granularity as of now.