From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F1681346FA5 for ; Thu, 5 Mar 2026 11:16:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772709371; cv=none; b=drA6+MWvlm1w053J+vl+xDysL2KXmcoccLttUurBwzV6iQ2uBJDUAia9Qi+vXKIftpv9NHlNqEhY2opAVZBP/i2vYrf7uVioJ9fN/9Qri7ThAKxlrf6B3Vr/o4ck7LR0IB5Dnx5yamBUBkgoHcHmPbc7b/H1h3Q95ID2YzyoeoU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772709371; c=relaxed/simple; bh=l1ZbtLyNA6lI9TKl3pAejIxhsysQof2e1Dze+vQ/AEE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=kLuONWxLSVCCJY6I8SV03MNmzRq1pZ0PHLivTaazmdyXrAJonelm2qDOk4b8eDGRHcbRTQWNkEze7RmAHcqxfbFsyPpn7TggVVth4QVgJ7oXj9XFh2HaG5meybCsKSAR1q5QVS3H+QEtPYxOaf+Q654g0zKH0C+V1aidF0niddk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Lxsip5ER; arc=none smtp.client-ip=209.85.128.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Lxsip5ER" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-483786a09b1so78529245e9.3 for ; Thu, 05 Mar 2026 03:16:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1772709368; x=1773314168; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=FAPg6eWb0oTea+TfR2D6Hy6n2JsKfxvodDgnN4a5J6A=; b=Lxsip5ERzOOLpXDXGDvcC1QdwolyJiMmlBerPqQ26MQcfOHtlkPn4M7MIt+/Vfpg64 wGVq6maJDIQ4SQxjk+np/huUuW6FmYpBLMs//ND7eGbvtPuC/UJO3ayii6HZQh3/gsHw 4k2FBIElGUPCnPkMT9Xftq9QuJjuP8MfuJhs8+ETTnoXqBZ6/D2X3DqTa28cFfhssqwt //Z7zG5MPCTlM1M0cyf3YGre2HJ3UtrZC+ZkoWPAZCKQZCQQ3b3bjh+7yrlrl7hoguLp SWIjOhVBY1M4dNFfxJ2+fSDzEexqoAEIpEs598vuhEuA/ATh7GKKiIGRMpsUZf7PqUlY QWEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772709368; x=1773314168; 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=FAPg6eWb0oTea+TfR2D6Hy6n2JsKfxvodDgnN4a5J6A=; b=JkjvT4C55jHqY6t++h6SQGvTUtLgRG/QAFMvhBov09mZ1POfEyz07fvMlnJJWCll35 vDlYXq6gOVbee//SUmwYnDSsAmTfcd+xgDst4cLK6qSiuoOQVYJ3Ab4GNEGBaPA26Fz0 B+xoUP8UyKAoLCjtluS+4711yTl4a3VKzST57PTzhF4GUELjpNqGGAMIzkS5IrjuChWE Vwy/fdt+bamIXxovZeRMoAX6rwNK7GhE3uR3yz4haBYg0Ii8LF9++vPh9eXae74lWczB yHrNN8p4O2HX3x2wMZKbPDVoIAQnt5TnTIVg8jIiv/ephUats/5M0sEnnhQCJCWbda4b YocA== X-Forwarded-Encrypted: i=1; AJvYcCXBwE9HqyK9+M29bugd8PlKAuwrR0wO7OJeaUGtRCVAJUv0V3PBlA6g3WNz5IZxNzAhFP8MNmZaccoJnCY=@vger.kernel.org X-Gm-Message-State: AOJu0YyNThBFffwqYfg7jLTtoE5kzAkjkYhOxgKg1VxAafglbXFhwSDL tFbbfJQZXMzAEzt69qFCRm9HV8ysWIlrkOrmxVj5+FJqdkQZNfr9KXcm8R+FckdTsySIW3XdRxu o9y6+vz3OpgL4QA== X-Received: from wmsr1.prod.google.com ([2002:a05:600c:8b01:b0:483:944a:4936]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4e11:b0:480:6c75:ddce with SMTP id 5b1f17b1804b1-485198b33a6mr103114855e9.33.1772709368216; Thu, 05 Mar 2026 03:16:08 -0800 (PST) Date: Thu, 05 Mar 2026 11:16:07 +0000 In-Reply-To: <6206d021-e6c2-4899-b426-cacd71ebd5ef@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260225-page_alloc-unmapped-v1-0-e8808a03cd66@google.com> <6206d021-e6c2-4899-b426-cacd71ebd5ef@kernel.org> X-Mailer: aerc 0.21.0 Message-ID: Subject: Re: [PATCH RFC 00/19] mm: Add __GFP_UNMAPPED From: Brendan Jackman To: "Vlastimil Babka (SUSE)" , Brendan Jackman , Borislav Petkov , Dave Hansen , Peter Zijlstra , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Wei Xu , Johannes Weiner , Zi Yan Cc: , , , , Sumit Garg , , , Will Deacon , , "Kalyazin, Nikita" , , "Itazuri, Takahiro" , Andy Lutomirski , David Kaplan , Thomas Gleixner , Yosry Ahmed Content-Type: text/plain; charset="UTF-8" Hey Vlastimil, sorry for the delay I've been unexpectedly out of office. On Mon Mar 2, 2026 at 3:36 PM UTC, Vlastimil Babka (SUSE) wrote: > On 2/25/26 17:34, Brendan Jackman wrote: >> .:: What? Why? >> .:: Why [RFC]? >> >> I really wanted to stop sending RFC and start sending PATCHes but >> getting this series out has taken months longer than I expected, so it's >> time to get something on the list. The known issues here are: >> >> 1. __GFP_UNMAPPED isn't useful yet until guest_memfd unmapping support >> [0] gets merged. >> >> 2. Apparently while implementing the mm-local region, I totally forgot >> that KPTI existed on 32-bit systems. I expect the 0-day bot to fire a >> failure on that patch. > I don't think you mentioned (at least in the cover letter) the mm resistance > to add new gfp flags due to number of them being uncomfortably close to 32 > already. But I see you've put the new one behind a config. Together with > point 2 I wonder if this is where we can start making some flags and > associated functionality 64-bit only and change gfp_t to unsigned long? Yeah, making __GFP_UNMAPPED 64bit-only would be fine with me. Ultimately the fact that we have KPTI for 32-bit makes it sound like we would also want ASI for 32-bit, so I guess I would still want to add a GFP flag to support that on 32-bit. But that's a pretty futuristic problem, I would say we should focus on __GFP_UNMAPPED in isolation right now. (Just to be clear regarding point 2 - that bug still matters, even if __GFP_UNMAPPED itself is 64-bit only the mm-local region is separate and needs to be correct on 32-bit).