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 18ABCD10F20 for ; Wed, 26 Nov 2025 10:19:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 61A0C6B002D; Wed, 26 Nov 2025 05:19:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5CAAD6B002E; Wed, 26 Nov 2025 05:19:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4B9C76B002F; Wed, 26 Nov 2025 05:19:41 -0500 (EST) 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 341F46B002D for ; Wed, 26 Nov 2025 05:19:41 -0500 (EST) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id DECEF89612 for ; Wed, 26 Nov 2025 10:19:40 +0000 (UTC) X-FDA: 84152361720.17.3F99613 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf12.hostedemail.com (Postfix) with ESMTP id 096AF40019 for ; Wed, 26 Nov 2025 10:19:38 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=aVwJbqF5; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764152379; 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=Nv0Ia9Ab7WWEHHM0k3Im5+0Yircf5KaIa7EgL+leHIM=; b=45/kzNFdLjgQQEm4g5WpBC1T8OCsPdTu4FTNxU/lZpoEY1QI3p3EDCw46qo7/EYFjUrwRE dtqTvfTJO8wWoXdrccVfS0pM9dwtXVZK/V5QRRa5svS5EggT4ZpiMHVWFMpI+dXVyIrp2F YAjEteBFiyoWkXNF1+be+6gea19wSTk= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=aVwJbqF5; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764152379; a=rsa-sha256; cv=none; b=I7ZPXXB2Zgvjz4dABfCoNw+AlwnaHwgL9ptxfqFa7r5+xZAmDtZexgHXjWAaNjh1zOzAoh y0YsHcr33j7wi9ikJFlz24anJJK9l7dZCQvJEShecJLu3XA9BmU5mtoZnBTblKN2nHRG7T Az+jts9S7L2z2pwYmhPVXT3MkYzg6yQ= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id DB3ED44477; Wed, 26 Nov 2025 10:19:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA3A2C113D0; Wed, 26 Nov 2025 10:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764152377; bh=e9FOp73QbX/qH1ICAIHKKQ91Oue3tJPhRgVdlzZS0s0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=aVwJbqF5LwtL/GBKSUM5lJlYOc5Cq82JW3QAUHKZUy6XidPIAMiJBSP3E4lH2cDHG X2Ly6ckgxDIJj4VnA4AZ02oTyXeySLUkMQ51x4rI1m7tbW8hdSz8VLQAYDgA3yquMO u6becA6wo00CKuOCaiqLIYWeKbFktTC6jhiALlraSWGCnAx/bKsccS7Y0ipgbUSIUc 6ZhvqjZbMYnY+1beJ3/ghajKkAq2PTzStQyj+UpyKGe4FR6G4z6+y4u+49klpKMLqS nFA73WD+j0GyBzg6b8/ljzsvszZFDzmfMTUq/CQKql4wVXnHk3ariH1xzaNjIjwGu0 Gux6LkgjkAB3Q== Message-ID: Date: Wed, 26 Nov 2025 11:19:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/5] mm: introduce VM_FAULT_UFFD_MINOR fault reason To: Mike Rapoport , linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20251125183840.2368510-1-rppt@kernel.org> <20251125183840.2368510-4-rppt@kernel.org> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251125183840.2368510-4-rppt@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: h1nedmpayph17c9qu8ha8n35jan5s19h X-Rspam-User: X-Rspamd-Queue-Id: 096AF40019 X-Rspamd-Server: rspam09 X-HE-Tag: 1764152378-349829 X-HE-Meta: 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 S+LHP3pY kUJeipqO9pqp92DgW6Q7TAwfepVFBx5C9EJ6m5zzUHtNB5GPFiU0UB0T6PXZcR6IILZBbGfd0i6IujtmQjeoCzlPd7hbS2DOuiVUJ5s1QXw3rWAlZxuFJslPg6CAxfcvMQaLF8gBb6IBF9XxjM7MDDL7XOWPChnq6Or+UtZlmeJKiJKu1gkQY2cm8RDrXea/TA135ClBDS6yE7y9uuK5m9AfTOFXqhNnItXhNBbTMloe7ZtUZxy62naDr/A2Uy5WQXstk9AtDF3hFAkEDaPxEsDW/CEiUoLwXc6ZzmPba3K6QJLayyVY5YbyJoQ9Y73x9ZCvHDXSr/ROrinEeqOskZPAnAQ== 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: > @@ -1564,7 +1571,8 @@ enum vm_fault_reason { > { VM_FAULT_FALLBACK, "FALLBACK" }, \ > { VM_FAULT_DONE_COW, "DONE_COW" }, \ > { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \ > - { VM_FAULT_COMPLETED, "COMPLETED" } > + { VM_FAULT_COMPLETED, "COMPLETED" }, \ > + { VM_FAULT_UFFD_MINOR, "UFFD_MINOR" }, \ > > struct vm_special_mapping { > const char *name; /* The name, e.g. "[vdso]". */ > diff --git a/mm/memory.c b/mm/memory.c > index b59ae7ce42eb..94acbac8cefb 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5279,6 +5279,8 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) > } > > ret = vma->vm_ops->fault(vmf); > + if (unlikely(ret & VM_FAULT_UFFD_MINOR)) > + return handle_userfault(vmf, VM_UFFD_MINOR); > if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | > VM_FAULT_DONE_COW))) If we want to reduce the overhead on the fast path, we can simply do if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | VM_FAULT_DONE_COW | VM_FAULT_UFFD_MINOR))) { if (unlikely(ret & VM_FAULT_UFFD_MINOR)) return handle_userfault(vmf, VM_UFFD_MINOR); return ret; } Maybe the compiler already does that to improve the likely case. LGTM -- Cheers David