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 DEEF5C79F9F for ; Thu, 10 Sep 2026 11:36:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DF0AD6B0099; Thu, 10 Sep 2026 07:35:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DA1546B00A2; Thu, 10 Sep 2026 07:35:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C73CB6B00A3; Thu, 10 Sep 2026 07:35:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id A69C66B0099 for ; Thu, 10 Sep 2026 07:35:59 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 43BAD1A04D9 for ; Thu, 10 Sep 2026 11:35:59 +0000 (UTC) X-FDA: 85197648438.17.28A8B9A Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf11.hostedemail.com (Postfix) with ESMTP id 5BAF340005 for ; Thu, 10 Sep 2026 11:35:57 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=arm.com header.s=foss header.b="CgX/mRT0"; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf11.hostedemail.com: domain of yeoreum.yun@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=yeoreum.yun@arm.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789040157; b=MWUSMIZmUWAtTJC7XaJRQKEOS1wQuO7NsU/oKvd4chYq0QgdDERGzD3k6J0cshZK4HklBt JhAhN9Zj22/2hp6Z2jp95+g41S+nUU5lfobw+nGWmVPeCig1Nc0PvmzPQm3Zvn4DbA+Drf mnHTMhAGUit41WnQopXHMOeAEyM45/M= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=arm.com header.s=foss header.b="CgX/mRT0"; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf11.hostedemail.com: domain of yeoreum.yun@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=yeoreum.yun@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789040157; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=0yQR10rXGyLsWv+o0cxAuGH//hC3EjmuljRwX/a5Yjs=; b=QG0Wyrg2gH3aHx0d8b7PDyvukzC4w9uawdwZXuv3tq8c+QKHGFaGgcb/2rf7V1uJPdfcy3 v02zDEQRHAMf/s4wA5KJ3xMhh2Ea/Psxj59fPtsq0SItSPter6nxe5cfHcbJz/i/dp7556 rD4WofojM+eunVP7JVCmEgnlZpmoU/o= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BE4EF153B; Thu, 10 Sep 2026 04:35:52 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E863B3F528; Thu, 10 Sep 2026 04:35:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789040156; bh=aczfw/OR9qUx8B3t8k1OQ/240hod4So0X5+xLV4/xTA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CgX/mRT04r6IGfuQdDy64iV7rk9c3tmgqtkbP4fAHIXXQyY1qGDmqhzrIGyBV/x4d 6VCv3Ejrr5df0vlUe/MKPJyXEN0lFj6n7DXxd5v6HhF8nC2JCBMcBt1BitEZZ0JtGb G6tL2+pAkuCeWX/2qbtSouG74LXKcFbRexY4TzWA= Date: Thu, 10 Sep 2026 12:35:50 +0100 From: Yeoreum Yun To: "David Hildenbrand (Arm)" Cc: Yeoreum Yun , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 0/3] kselftest: mm: fix some failure of split_huge_page_test Message-ID: References: <20260907-fix_split-v5-0-822b810458bc@arm.com> <21e0a933-63b6-42b4-8cd7-df05b0c9acfc@kernel.org> <9750125c-49b4-48b1-adab-3a1cbec4255a@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9750125c-49b4-48b1-adab-3a1cbec4255a@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 5BAF340005 X-Stat-Signature: uef4uk6zpmujq41zm368qrfnf1ngxkp5 X-HE-Tag: 1789040157-396921 X-HE-Meta: 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 bOMT0Rf5 BQOf9uwIZy5foRVVOW+jPbTeQ3s/xIsHK0Ey3/m347tU/PRc2Z2VkcE81G4qYSc55s3cyWhKOe74hf+Sz3gkDIQCoEO8oLhYCf6j7Q/uvQtd2VJOzc3XPJFZmi3YRlot8tD5UH3/HAehugnjlliCJlTVw/ON40k5CSL3oZxfs88nHIjQPO0ZPT8pfuQ0YJz3Xow1HgQp4yJkoMWLXoIvTOCQARbxJBdQ2Ox7yv7Qf/IJrlIFj4Q5RjU2QUyiELOQJU2iSIGMYXVjs+ZwxJi1fBoSgh36227j3n6VU Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 10, 2026 at 01:23:15PM +0200, David Hildenbrand (Arm) wrote: > On 9/10/26 13:16, Yeoreum Yun wrote: > > On Thu, Sep 10, 2026 at 12:45:39PM +0200, David Hildenbrand (Arm) wrote: > >> On 9/10/26 12:31, Yeoreum Yun wrote: > >>> > >>> Well, users currently for using /proc/self/smaps are for check vm-flags: > >>> - guard-regions where using check_vmflags_guard() > >>> - pfnmap test where uses check_vmflag_pfnmap() > >> > >> Most vm-flags should not be an issue when it comes to merging. The only > >> exception are vmflags that do not prevent VMA merging. > >> > >> So it's VM_SOFTDIRTY and VM_MAYBE_GUARD. And I agree that for guard-regions.c we > >> likely have to care such that we don't merge by accident with other VMAs (guard > >> regions). > >> > >> But that's independent of memalign. > >> > >> ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0); > >> ASSERT_FALSE(check_vmflag_guard(ptr)); > >> > >> could be problematic on its own (unlikely but possible). > > > > Yes. That's why I'm think it would be good to use alloc_isolated_mem() > > in case of ANON mapping for this case. > > It's really only guest-region code that needs this. > > > > >> > >> For other flags, you really only have to find the smaps area that covers the > >> given address and look at the vm-flags. > >> > >> Or am I missing something important? > >> > >> (merging vnas with VM_PFNMAP is impossible right now IIRC) > > > > No. what I want to say including the patch #3 is for the above case > > where you point out -- ASSERT_FALSE(check_vmflag_guard(ptr)). > > > > Since we don't have any interface to check vm_flags execpt smap > > and for memory mmaped with anon would have a chance to merge, > > We need something to replace memalign() with preventing unexpected VMA > > merge. > Only for the cases that actually really needs this, which is in my understanding > guard-regions. > > And I repeat, this is not a memalign() problem. Yes. I'm not claim memalign() is problem but want to prevent unwanted VMA merge. That's all. And as I mentioned in another reply, if we get rid of ASSERT_FALSE(check_vmflag_guard(ptr)), this patch would be droppable. -- Sincerely, Yeoreum Yun