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b=WeA2TjZOe252OirCjUywfqcZhOukVCQvwiAHJtWHyVmFUAAtqWOmcQZgciXa8JJrJ q/ZBtuLQ3sNNx1VLbeZPq6wV7PV5Wz2B64GalSZMQsyPA0aB5RJUGXkAnE9MIGCRPE xijPvXqEOr4SkaBWkh1OJyozMqeUZBsQyG6B7TCiAscSEvRRQECcXBqtnU4Vb6Av/n NjrqF2kLUdV94fv4YvI/U3uXlRanXVi9JbtmBQc9pB5hW+Dpf04+9UJovjOc+ThTJX v3bkXiNj6AcRzN9uWUBdNo3wdep5gkAbgNt3mn7ij0zoXWGpxR8KuwR3c9Zj2CCucG IkocKl/ql8Sgw== Message-ID: <76f24730-46de-4583-9189-ff7ba28c741d@kernel.org> Date: Wed, 8 Jul 2026 13:27:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm: Standardize printing for pgtable entries To: Ryan Roberts , Anshuman Khandual , linux-mm@kvack.org Cc: andriy.shevchenko@linux.intel.com, usama.arif@linux.dev, hughd@google.com, willy@infradead.org, Andrew Morton , linux-kernel@vger.kernel.org References: <20260708032824.969752-1-anshuman.khandual@arm.com> <25cde246-540f-4ab4-b541-0b7313c57954@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: <25cde246-540f-4ab4-b541-0b7313c57954@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: fe845k3j6j31op93ec4uy8gsnk3ubjgn X-Rspamd-Queue-Id: 27F3BA0002 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783510049-60086 X-HE-Meta: U2FsdGVkX191MciVXiD7VfK24xXSo9rV/I1mO9xMlJUVLqDWnlbrprB6/4RDRwVboEgKqQDLMNne7wj4MBbsS61MBqph9yFkhqrDY0omi6iaZEFh3tDmSEHjjzNGyqyM+7XR+/vJyD0mXqwzwdGSi5TjjfrQ6mPTwEKWYxIQQ0rgBjwbEvmtMUsAvpIYQP+Xqs5oMYYPXTC2h+hf104nTbqIYvhP1ebC04WXYC+ePElmDYMVsNOTV6tNiCCKXrL3nfltfxKtBcBDdYVFpf16lhr3thuJPQ6cOAx3BJBvYQBpkTXK1ipeI1W8mly5ONsnzWDhxvSt/LILLQk/GWp08S/nyPF4mOvx6wSkj9Q1rInRi4hNX23DBSoJd6nwHCjkNpWaZS7bhhrdWA0jngwhssYbp0me96uvJNSlP6NYcHzuEo0CpRzb8nIIlTva2MZbbaWyoY1rm6ACyEpz/YWPHaB5p8eHRmw46ss/wBWvpFAHH8F15tWGZCz0O2IT/wnD7mK+E+NR9pvanz9+NHySmYW+I2JHcXRTXUxmufoUiJ4dy6jVivtI1fVRBa06oUNA1sP/t9wV6Y1Q2Vc3EijSPdjrfVyCosdhsHQwaAfKIGqTOeA5F1mlbUVaLDT19/cQU5Vfqa5Qs4h1mGFqhXeK028JeRObfzFONkn30lAhEo/nuFGDNKNpcJRWCRLvENwkPOucV0Ra2AqHrq/2LsHwbQNBMd/tVLzyfV5o68iysHGyrXKWSAMc4DC9b7KeswCXOqWZ+gji8N2C1BI7QJqnHIF68u1WuWLat9tklMButlsYcNTSJl0mqcEHK7qq7yRrl6+Jo8Vh+R3RnZf2Rj2lLrXl0y9fZPOUgkRzH1HVdu+eKsVa9+hRNiWsUbnbU2Yzst1+xlCAkGKNGL0Bhv437cX0Vd8PJye1NgRCBBlVVvCbAZOUlLcoEiZ3/+Ew/FxraMkJ33rC+kTjaYaciPL 3cpK0BZo LdyktSiySdnr8FwozE/4WB+NAPfnhHdfZU2Gtt75kGkKJBwSRFz9OEUaE9nJbtd79M1jq7F/bzkL5OS2mAxj+rrqOyJ4quYw9J4hfxS7vqP/0J0bvjKKDBGwt0v6bk69tDHgPTOMjn/hvtNxCIhq5Lne98b+xgi8WaIu+dJWg1SIkXkEBI8dGLG7t6Mp+zSKgjZUjINQbJJxv/7e2lhNQXlxmfDy0IcDE3EWnZ+mmxsHjembdtUJfzMiY3RToKq9JIIWoYrrz7WVm0xRe3vJCASHcSw1xZ4chxpE2eKeJ/KQN80KbrF5GtRV03stUlW8RLzBSFzOa8EDJew9abY6dkLBMVarVBhRhudeLFBowvWLZ6nrYlcxgizwgjYRItPs2yNz5mQbpfvyT0dtjY7dfXCSokRhLsYZEZdtLCaLsM81YLrBXknkSpSuKmsgpVEdtEJuMdZrglcheVtc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/8/26 13:22, Ryan Roberts wrote: > On 08/07/2026 04:28, Anshuman Khandual wrote: >> From: "David Hildenbrand (Arm)" >> >> Bad page map reporting currently stores page table entry values in an >> unsigned long long and prints them with fixed 64-bit-oriented format >> strings. This is inconsistent across call sites and does not work well for >> architectures where page table entry values are not naturally represented >> as 64-bit values, such as 32-bit or 128-bit entries. >> >> Introduce a common helper to convert raw page table entry values into a >> fixed-width hexadecimal string based on the actual entry size. Use it for >> bad page map reporting and for dumping the page table walk in >> __print_bad_page_map_pgtable(). >> >> Pass page table entry values to the reporting path as raw bytes together >> with their size, instead of forcing them through an unsigned long long. >> It keeps the printed output consistent and avoids truncation or misleading >> formatting for non-64-bit page table entries. >> >> Cc: Andrew Morton >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: David Hildenbrand (Arm) >> Signed-off-by: Anshuman Khandual >> --- >> This patch applies on v7.2-rc2 >> >> Changes in V2: >> >> - Dropped space after ":" during print per Matthew >> - Dropped CONFIG_CPU_BIG_ENDIAN per David >> >> Changes in V1: >> >> https://lore.kernel.org/all/20260707041703.658021-1-anshuman.khandual@arm.com/ >> >> mm/memory.c | 98 ++++++++++++++++++++++++++++++++++++++++------------- >> 1 file changed, 75 insertions(+), 23 deletions(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index ff338c2abe92..a2b63af82792 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -519,9 +519,48 @@ static bool is_bad_page_map_ratelimited(void) >> return false; >> } >> >> +#define PTVAL_STR_MAX (32 + 1) /* Max 128-bit value in hex + NUL */ > > Not sure if it's worth doing something like this?: > > #define PTVAL_STR_MAX \ > (MAX(MAX(MAX(MAX(sizeof(pteval_t), sizeof(pmdval_t)), \ > sizeof(pudval_t)), \ > sizeof(p4dval_t)), \ > sizeof(pgdval_t)) + 1) > > Would probably save stack space for 32bit arches? Do we really care about that? This is about a corner cases error reporting right now. > >> + >> +static void ptval_bytes_to_hex_str(char *buf, size_t buf_size, const void *entry, size_t entry_size) >> +{ >> + if (WARN_ON_ONCE(buf_size < entry_size * 2 + 1)) { >> + snprintf(buf, buf_size, "overflow"); >> + return; >> + } >> + >> + switch (entry_size) { >> + case sizeof(u32): >> + snprintf(buf, buf_size, "%08x", *(const u32 *)entry); >> + break; >> + case sizeof(u64): >> + snprintf(buf, buf_size, "%016llx", *(const u64 *)entry); >> + break; >> +#if defined(__SIZEOF_INT128__) >> + case sizeof(u128): >> + snprintf(buf, buf_size, "%016llx%016llx", >> + (unsigned long long)(*(const u128 *)entry >> 64), >> + (unsigned long long)*(const u128 *)entry); >> + break; >> +#endif >> + default: >> + snprintf(buf, buf_size, "unsupported"); >> + break; >> + } >> +} >> + >> +#define ptval_to_str(buf, val) \ >> + do { \ >> + __auto_type __val = (val); \ >> + \ >> + ptval_bytes_to_hex_str((buf), sizeof(buf), &__val, sizeof(__val)); \ >> + } while (0) > > I think arm64 code also does pte printing, which you also need to fix up for > D128 support. Perhaps this could be moved to a header for reuse? We could do that as a second step, right? > > Also not sure if it's worth returning buf so that this pattern would be possible: > > char pmd_str[PTVAL_STR_MAX]; > pr_err("pmd=%s\n, ptval_to_str(pmd_str, pmd_val(*pmdp)); > > Although perhaps that's a bit busy and should be discouraged... Yeah, let's not do that. -- Cheers, David