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 B20FBCD6E56 for ; Wed, 3 Jun 2026 11:41:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 296A36B008A; Wed, 3 Jun 2026 07:41:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 26E736B008C; Wed, 3 Jun 2026 07:41:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1AB686B0092; Wed, 3 Jun 2026 07:41:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 0B0CE6B008A for ; Wed, 3 Jun 2026 07:41:53 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id AD4D41C1600 for ; Wed, 3 Jun 2026 11:41:52 +0000 (UTC) X-FDA: 84838412064.26.FE9211B Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) by imf14.hostedemail.com (Postfix) with ESMTP id BFE2410000C for ; Wed, 3 Jun 2026 11:41:50 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="M4Wz5t/G"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf14.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.184 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780486911; 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=UL4u4uRmoBKLAhYy0Fqp9Y3r55rWdaL145K+bUKWQuc=; b=cWkq7DOUzDFIsNxmSc7DYB2HmYxoUzEXNjFsuSYO2fn4JGbnjfSA2aLL4XmCYGc0AiV/zQ 7BJ2LACgybqn/a6T9DFCrwIyNWtOzzO35YbKxGglf9lr0YFsjwi0+f/PIsiBo3+VilcIVt 6rz8X5/vMcie2EhS3kH0wcLDwyg+7EA= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="M4Wz5t/G"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf14.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.184 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780486911; b=j0wL36zYHfsME2C+OKt8P8GYwnF+C1DQmtTrjQTNOWDReXFx0s88q4L3U6bHMu6vQY8OhC 9zuXKjz+t4s7fRIxlMefNChd7Jfj0P4hmN4ePu2pa8/GgnvEAcU325q2xUQNB3Yc6isbbq Ir1HrYPaswRWU8P9JkgT3bbjsz/jwVE= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780486908; 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=UL4u4uRmoBKLAhYy0Fqp9Y3r55rWdaL145K+bUKWQuc=; b=M4Wz5t/GibhfnNJucsvpMWybJ8N37f+NtPwNfqQbWUp/F2WviagIn1AYil01IjdZrdH1qZ KvJ02tTXvO8DRDlAUekPBpw55zsTAYV6lHYBRuG98UTQkk6MtthrQqBvLyNVCWplx6l9cx goCRkPNpH4YfnMx953wYvBWXY59ao1U= From: Lance Yang To: rppt@kernel.org Cc: lance.yang@linux.dev, akpm@linux-foundation.org, david@kernel.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, xueyuan.chen21@gmail.com, ioworker0@gmail.com Subject: Re: [RFC PATCH 1/2] mm/secretmem: try to restore large page mappings in direct map Date: Wed, 3 Jun 2026 19:41:34 +0800 Message-Id: <20260603114134.3010-1-lance.yang@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: 616soyqqxz9ikmgtfwsuyemuw6b7bpxn X-Rspamd-Queue-Id: BFE2410000C X-HE-Tag: 1780486910-836686 X-HE-Meta: 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 1ki35ho1 55xjdbmT0ULYd4TGqP1o85bwBD2CnO/C59j+lWyGIWO/qbkhaV0HnKOmL/oo0CINcRfMxPXobnMkqW/GtuZjtdIx5X4J3oU3/qBmgaIhS/F7Y4g+eyEna+o+zv6QC5tnueOCAd0mncZCbPb4HoC3S8GquIS0oZKUfDfCseObBwYI+4Z+6y8+OvPpkAet5HuRmQFLAdSUIPMJkIiHpk8GRAY5xUNuYhNfCdNfSTJMiAZeN68iKms6+ZKd+8d1cX4KBY52fB1Kug4XsSargrTdy5EVp7Oq8qudpRqGnUD/pxeo2er+BCM4IFj0xNbRwBrkn3QjAJlv2AQ4djZc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jun 03, 2026 at 01:59:39PM +0300, Mike Rapoport wrote: >Hi Lance, Hey Mike, >On Wed, Jun 03, 2026 at 06:46:23PM +0800, Lance Yang wrote: >> From: Lance Yang >> >> secretmem removes the pages backing secretmem mappings from the direct map. >> >> Removing one base page from the direct map can split the covering large >> mapping down to PTE mappings. Repeated splits can leave more of the direct >> map mapped with PTEs, meaning more TLB entries for the same range and >> potentially more TLB pressure. >> >> So let's try to restore large page mappings whenever secretmem restores a >> folio to the direct map. >> >> Tested-by: Xueyuan Chen >> Signed-off-by: Lance Yang >> --- >> include/linux/set_memory.h | 6 ++++++ >> mm/secretmem.c | 12 ++++++++++-- >> 2 files changed, 16 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h >> index 3030d9245f5a..ad2fa414a22d 100644 >> --- a/include/linux/set_memory.h >> +++ b/include/linux/set_memory.h >> @@ -58,6 +58,12 @@ static inline bool can_set_direct_map(void) >> #endif >> #endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */ >> >> +#ifndef arch_try_collapse_direct_map >> +static inline void arch_try_collapse_direct_map(struct page *page) >> +{ >> +} >> +#endif > >Did you explore what would it mean to hook collapse_large_pages() into >set_direct_map_default_noflush()? Good point, I kept it separate on purpose :) Putting collapse into set_direct_map_default_noflush() would change the semantics of that helper a bit, IMHO. I would expect arch_try_collapse_direct_map() to also be useful for cases where a direct-map permission change could split a large maping first, and the user wants to try restoring the large mapping after changing it back. One example[1] is making a direct-map range read-only for security, which I am also working on :) [1] https://lore.kernel.org/linux-mm/9979fa87-88ef-4baf-8592-502ff4888085@kernel.org/ Cheers, Lance