From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E621E47425C; Thu, 10 Sep 2026 11:55:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789041310; cv=none; b=Dpz0ljk+rSgph+rBmY2H1Zl2LiTIVRhT9vJu5V4Me1oS6QfRKQWLikNUTPQ+nmLCk/tIwlUXtPECzPL2H0fJwaWd053moXVM8JOquxWRPwMZftz5IyiUre4TIk+IMSskYMHPvv0ZnK3Kq+Mwp5VxJWhTeh04MGK0FH2lx7US5Sc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789041310; c=relaxed/simple; bh=08vR67eDLLam5Ol6PmipNh2+kA+2F9Qr6vOEB9hurTo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=P3C+bSZNbSgVyvExyGLSV8QiuV2Gchp1z212I5xyaGvajtyiYnByEUp2eE5Tg/scx8CtvvAqAfYSF73IprjHPUrT8kvqruzBbCj8vvckrt+Pg15VeZ22jIJkEJEH0FR9fBS9ml+PqtajjNKgmu08vVFuJDWLBPOnDgxItHT85+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FYsoNed8; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FYsoNed8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64FB11F00893; Thu, 10 Sep 2026 11:55:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789041308; bh=HndTqnttNHPeJm/zRQ/NFvgMrbPvSUK2ZR4N90t4mPU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=FYsoNed8dt8TFC++FzMGu0IQeDK2UoI3RLPtEpoT0pnBrmFQ1lOa3rVFou475gEXs wkFbUQIkNQaEcJ4+QS3+FnqJvWKEJvRtuzkJUsXSY2kZpsIK8lTJPV9eikYrB4eU93 /bv0s5gJ2ijqFZiP73TUy2y6jmcGaVKL18zOTa5XILUKhdFUv2XgvTmslSxveItrBK KMaS+cgEmgwRfu3KPSyCkmlhQ0xnc/LNefctnBfIhP3DdD5/E9dc+rkiVbROsBg6ah FBNPRGq+N1xZ5ooO4fEvSi2/N0497/4dM+qJLv1rJFSLIMJzE33zke+VznPP0rnZgT PKVhV8f+YzOrA== Message-ID: Date: Thu, 10 Sep 2026 13:55:00 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 3/3] kselftest: mm: introduce alloc_isolated_mem() To: Yeoreum Yun Cc: 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 References: <20260907-fix_split-v5-0-822b810458bc@arm.com> <20260907-fix_split-v5-3-822b810458bc@arm.com> <5c05b620-7a2f-453d-9725-fed4f536a019@kernel.org> <31418d0e-9745-4e8d-bc02-dbbd5cb9e193@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/10/26 13:30, Yeoreum Yun wrote: >> On 9/10/26 13:22, Yeoreum Yun wrote: >>> >>> As I mentioned in my previous reply, what I’m trying to prevent here is >>> a failure when checking, immediately after memory allocation, >>> that a specific vm_flag is not set. >>> >>> Yes, I agree that this could have been a problem even before >>> the internal changes to memalign(). An unwanted VMA merge could already >>> occur at the time of memory allocation. >>> >>> So what I’m trying to avoid is a test failure where, due to such an >>> unexpected VMA merge during allocation, the subsequent check that >>> a specific vm_flag is not present fails. >> Which is only a guard-region marker problem? > > Yes. so if we remove ASSERT_FALSE(check_vmflag_guard(ptr)), TBH > we don't need this patch unless other usage comes up to prevent unwanted > VMA merge. > > Would it be better to drop ASSERT_FALSE(check_vmflag_guard(ptr)) in > guard test? I guess there is value in asserting that not all VMAs by accident start with an over-indication of maybe having guard pages, which is why Lorenzo added that check :) But I think even alloc_isolated_mem() is wrong in that regard: if the original VMA gets merged, we could inherit the guard-marker, no? Maybe the following would be good enough? diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c index 5c8ec3ca75d7d..791bf6a68b9e6 100644 --- a/tools/testing/selftests/mm/guard-regions.c +++ b/tools/testing/selftests/mm/guard-regions.c @@ -2257,10 +2257,20 @@ TEST_F(guard_regions, smaps) char *ptr, *ptr2; int i; - /* Map a region. */ - ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0); + /* Reserve a 10 page region with 1 page space to both sides. */ + ptr = mmap_(self, variant, NULL, 12 * page_size, PROT_NONE, 0, 0); ASSERT_NE(ptr, MAP_FAILED); + /* Map a new region that is guaranteed to not get merged in any way. */ + ptr = mmap_(self, variant | MAP_FIXED, ptr + pagesize, 10 * page_size, + PROT_READ | PROT_WRITE, 0, 0); + ASSERT_EQ(ptr, ptr + pagesize); + + /* Clean up the excess pages left and right. */ + munmap(ptr, pagesize); + munmap(ptr + 11, pagesize); + ptr + = pagesize; + /* We shouldn't yet see a guard flag. */ ASSERT_FALSE(check_vmflag_guard(ptr)); -- Cheers, David