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b=pOXn5XWEcNoi0kYL+zqUzWF1ShgtL9v4L49YHqamUKLPOS5dtEVajb96mplr9Sbm8 yJQKqwE2l+kmf1oUWqMj+mx0dFXHPbo2TurFgO+o2e62qIxcy5fG22NHBZkoGmhlox mScGjjtimSHCSHDcu7uMjRAdKE8vLsrFohYmIiPIiOfpARyT0IEScy1f0yHnw1nyjr qdVXVx+W4+2ZLNi+XQ8EqTFfrbmFupYKgBoj+ECnPCLQxfutqCfCxVj21dKURnzdBN h3bPcjGOyw0YyoHXP+hq3VPfe8RGbpyBYS9ZoMZNJ/jt0WnAkP+ip0G9UgRonJDzK2 akxm3aT6u+I7A== Message-ID: Date: Fri, 27 Feb 2026 21:55:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/debug_vm_pgtable: Replace WRITE_ONCE() with pxd_clear() To: Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , linux-kernel@vger.kernel.org, Ryan Roberts References: <20260227061204.2215395-1-anshuman.khandual@arm.com> 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: <20260227061204.2215395-1-anshuman.khandual@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A95191C0010 X-Stat-Signature: bqe6dqd6ctmznwzmih3zb5339mssyr4a X-Rspam-User: X-HE-Tag: 1772225724-725788 X-HE-Meta: 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 jEKmHdgf evCa4v2bYa2ih3BwzBqgA7UAYmvQay6MtowWRhU+mK3pr5El6k7pCA3tiD+LjDWdJrBIldxWvAckCP/VJk9j8EGAzlW8EXr/qxIGcla9q5U4dVRAtlDVfJRd3NHo9OeAkA1wqmX6YIWQJ7QxPd7xr53B7RebN6wKWui+p/9N6htP/aygm/65sXIPrkoLxh4/rQa5FgAdrcjbnOBPhDYpU/B3Lz6E2Q3hnrHGYeyrYXeGM8hfXX/j2tQVS95EHuYVFeSdtf3kPFlXV1/m0RKH7EbDfc4NSkCb+XAcFsZX1587YFwHSAW46sF6GV28ZsZpAttzXdiXsqQhckWVE3UTi59UYN4AUm98l7GD/69F+W6StxiwV+2yZ8M4lEybLxwoqe7DNzgtChWEie/nU10oDc7VYxCuTUCPfKDXpdvSKh+Dh6b0G87DMmfWz0DaD2JINffmJ0rJlXXtSvc164zzRxYn0vGcNDxOLxEgQ5hB56gI7rV7gioNJuI2Mqw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/26 07:12, Anshuman Khandual wrote: > Replace WRITE_ONCE() with generic pxd_clear() to clear out the page table > entries as required. Besides this does not cause any functional change as > well. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Suggested-by: Ryan Roberts > Signed-off-by: Anshuman Khandual > --- > Applies on mm-unstable and tested only on arm64 platform. > > mm/debug_vm_pgtable.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 83cf07269f13..23dc3ee09561 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -445,7 +445,7 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args) > * X86 defined pmd_set_huge() verifies that the given > * PMD is not a populated non-leaf entry. > */ > - WRITE_ONCE(*args->pmdp, __pmd(0)); > + pmd_clear(args->pmdp); > WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot)); > WARN_ON(!pmd_clear_huge(args->pmdp)); > pmd = pmdp_get(args->pmdp); > @@ -465,7 +465,7 @@ static void __init pud_huge_tests(struct pgtable_debug_args *args) > * X86 defined pud_set_huge() verifies that the given > * PUD is not a populated non-leaf entry. > */ > - WRITE_ONCE(*args->pudp, __pud(0)); > + pud_clear(args->pudp); > WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot)); > WARN_ON(!pud_clear_huge(args->pudp)); > pud = pudp_get(args->pudp); On some architectures, pmd_clear() does not set the pmd to zero. See s390x as an example: set_pmd(pmdp, __pmd(_SEGMENT_ENTRY_EMPTY)); Which results on 0x20 being set. Maybe we're lucky and all relevant architectures do not have CONFIG_HAVE_ARCH_HUGE_VMAP. Or maybe it just doesn't matter. We'll find out :) Acked-by: David Hildenbrand (Arm) -- Cheers, David