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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD588C74A4B for ; Sun, 12 Mar 2023 21:07:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230398AbjCLVHm (ORCPT ); Sun, 12 Mar 2023 17:07:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231610AbjCLVHd (ORCPT ); Sun, 12 Mar 2023 17:07:33 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77F233D09A; Sun, 12 Mar 2023 14:07:30 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A963860FF0; Sun, 12 Mar 2023 21:07:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F00AEC433EF; Sun, 12 Mar 2023 21:07:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1678655249; bh=h87ZzwI3zuKwTkH2SQLxCZxmqB1ZqJ6gpFuwdGgxUfk=; h=Date:To:From:Subject:From; b=XPWYZg0wNcbfS7AAOvQ3+mqe3C7EMRWkrHLAvq59UXx830nWuFtVAVI1Po0OBpP70 nWy+S3DG5ESMKVIojhDWNDpLPILXF30DbncuQq0Rhn2HqLyGOQAp4wOxo3FKXiF2fu fsCRdeTfKImQ3xFuD+FHZC+L4jl7tgVDb4EE7Ln0= Date: Sun, 12 Mar 2023 14:07:28 -0700 To: mm-commits@vger.kernel.org, will@kernel.org, vincenzo.frascino@arm.com, stable@vger.kernel.org, ryabinin.a.a@gmail.com, eugenis@google.com, catalin.marinas@arm.com, andreyknvl@gmail.com, pcc@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + revert-kasan-drop-skip_kasan_poison-variable-in-free_pages_prepare.patch added to mm-hotfixes-unstable branch Message-Id: <20230312210728.F00AEC433EF@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: Revert "kasan: drop skip_kasan_poison variable in free_pages_prepare" has been added to the -mm mm-hotfixes-unstable branch. Its filename is revert-kasan-drop-skip_kasan_poison-variable-in-free_pages_prepare.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/revert-kasan-drop-skip_kasan_poison-variable-in-free_pages_prepare.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Peter Collingbourne Subject: Revert "kasan: drop skip_kasan_poison variable in free_pages_prepare" Date: Thu, 9 Mar 2023 20:29:13 -0800 This reverts commit 487a32ec24be819e747af8c2ab0d5c515508086a. should_skip_kasan_poison() reads the PG_skip_kasan_poison flag from page->flags. However, this line of code in free_pages_prepare(): page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; clears most of page->flags, including PG_skip_kasan_poison, before calling should_skip_kasan_poison(), which meant that it would never return true as a result of the page flag being set. Therefore, fix the code to call should_skip_kasan_poison() before clearing the flags, as we were doing before the reverted patch. This fixes a measurable performance regression introduced in the reverted commit, where munmap() takes longer than intended if HW tags KASAN is supported and enabled at runtime. Without this patch, we see a single-digit percentage performance regression in a particular mmap()-heavy benchmark when enabling HW tags KASAN, and with the patch, there is no statistically significant performance impact when enabling HW tags KASAN. Link: https://lkml.kernel.org/r/20230310042914.3805818-2-pcc@google.com Fixes: 487a32ec24be ("kasan: drop skip_kasan_poison variable in free_pages_prepare") Link: https://linux-review.googlesource.com/id/Ic4f13affeebd20548758438bb9ed9ca40e312b79 Signed-off-by: Peter Collingbourne Reviewed-by: Andrey Konovalov Cc: Andrey Ryabinin Cc: Catalin Marinas [arm64] Cc: Evgenii Stepanov Cc: Vincenzo Frascino Cc: Will Deacon Cc: [6.1] Signed-off-by: Andrew Morton --- --- a/mm/page_alloc.c~revert-kasan-drop-skip_kasan_poison-variable-in-free_pages_prepare +++ a/mm/page_alloc.c @@ -1398,6 +1398,7 @@ static __always_inline bool free_pages_p unsigned int order, bool check_free, fpi_t fpi_flags) { int bad = 0; + bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags); bool init = want_init_on_free(); VM_BUG_ON_PAGE(PageTail(page), page); @@ -1470,7 +1471,7 @@ static __always_inline bool free_pages_p * With hardware tag-based KASAN, memory tags must be set before the * page becomes unavailable via debug_pagealloc or arch_free_page. */ - if (!should_skip_kasan_poison(page, fpi_flags)) { + if (!skip_kasan_poison) { kasan_poison_pages(page, order, init); /* Memory is already initialized if KASAN did it internally. */ _ Patches currently in -mm which might be from pcc@google.com are revert-kasan-drop-skip_kasan_poison-variable-in-free_pages_prepare.patch kasan-call-clear_page-with-a-match-all-tag-instead-of-changing-page-tag.patch kasan-remove-pg_skip_kasan_poison-flag.patch