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t=1783500754; bh=uAiHJAZE3BqubfKAGYUb2cSq4Ujum8v596zy+Arjh8k=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=IYWfqZFrlKzG5iJWdiAYy8Ptr9ZiKtF297oeqWsyzNZFU8+kHFSNgiP4wWR1XJeth kVHXxWu0p9WOGoBY5ea8OjxfSnyXs4oHx+X+SZV7gEvLhLv7DAweZbxcQuMWh7YFP0 HaCb+F3BAfohvyWF8iVoTHICvidotVcMkxJgbKaosBSpXE5fyyp98dmNnONNNNflxI IxOUk3oSAt9wbFHXqGx9Viz0WSvr2TeNZVNlvhPEFYn1Qas3U6yvu1y6onmmlV6CJU H7DEGzMuv9MowPdqCzRY7dOG+ESkD7xFEAonn/8RPYvNwuIC5N9smGqFB9r7iifBYp a9wqYG7TCC6rg== Message-ID: <5d4a10a6-430b-4df7-9085-a5b39631c6ea@kernel.org> Date: Wed, 8 Jul 2026 10:52:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm: Standardize printing for pgtable entries To: Anshuman Khandual , linux-mm@kvack.org Cc: andriy.shevchenko@linux.intel.com, usama.arif@linux.dev, hughd@google.com, willy@infradead.org, ryan.roberts@arm.com, Andrew Morton , linux-kernel@vger.kernel.org References: <20260708032824.969752-1-anshuman.khandual@arm.com> <876c533f-6709-43a0-8595-143a8b9c9201@kernel.org> <437505b8-8616-4341-8d19-033d5b6b1d51@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 916A51C0005 X-Stat-Signature: wxghf1xx7h7ehf43uuf93h45dk8ggzbj X-HE-Tag: 1783500755-318973 X-HE-Meta: U2FsdGVkX1/BZIzfMRFrG+UfJf0Dq7bC0E/ykslMaYkVnTEIFIL7UivsEjZ1OruDhD0VRqQhs5I28fwcN9wZMKsuNUVE4MR5OIhOXBdOAio5rsD8k+CEzgeDYk2kZFvfslEWpBFUe8Eobi24s7DX8XkG9L9aTtH4n8YTFwwrGvp5BeYJQy+qqXkHi++zqJrnF8InaOT+HR60X4/J42HSHzkPffShYQ40NmhtqWo7DSfRdsj04EkfIxDydbGgcQdfQL1X6HnPQn8OZGfZTN/d8JEO31qY4EMk79gdzhjlbuKne9M3Hbdqt6Mi0vf38U4QruPaeULf9HllFfF6TT6omcyIitJVtkGFVm18nZ739oFk7OhPJELRHr+HPrY63Isb/9GWNUY5N12+w284D1gn/ymBatTD+JYY3s9LrVx2tCiLLXXQe++qM8mxTO99KGZH99DCzYuwOHnOfhTv3OcZUNDLbqfWqiE+QYwcq5OLvIBCEsmR8jNR4NzRCGrkm/0ljzyMfpM5H2ZQ+0pimiKrpQOAMTPFY16JZXlh/yPTwjQ9P/ryGos54x1fOpkWFre7xYuNmOYMsRB1IMs0ebOOn5YgWMIfEzqhYpqyXJsmtJj91mDjuLz0S6MnlCTIliXy30VqJ8qT6t3zH6ihOaERhXi+qWWPcAYcBIxkXtYzkcZigJ6bJnBVZeRrX5SdegfmrwUOak4Z3ghdxnLhM0LPHjt9V/dlNBuQKCRO0p1v6VPxh0ACrqLqvsgF6gJuNs+RJSEZPmwJVHx24c+bIim9U19OsqtlNyyBjnO5h2MzCAq2GbfZaQxlQWIoEqd9zM9mQQbDwpg1Nmz2R9lrpZuot6cxzaVOorJDyCfVoePUyWgdyxs/AS7X9BR7Qqrai/PqHGZRLmRL1FtTiQap86uKhbEe4VXkUn9ceHyCqf/c4SQzvBBEQaBWmSIgYux3XSNkt/QtFS33Jaef9Fqf1Ez CPFP+zvF RbUb/E2iqGk/l3pn+xvb9zcwlYLKdA/ZdaJknD4WAy5/AY1E+b3AJirVg/SqV7pSF/hWHBKdQR9t8PpnfnvIC7jB2OBbBDUhVCNFyvk9jzH2pkmuqfhLtO1oPGdk7JZud27CINDAtO0eQtAIC3E/eXsNKnLtd3Ky43DaP2sb5HliwfQ/4EaBoUNdSUkOXTlvORt8GgzlWQd7c2ecl7V+UwsnkzRiDFkAaEvUAogRZNzkcfmZKZMwXz3P57+XWc8AHlYQ4v2FPHDdCesPVD+tt/atfmxJkU/X5N5Kgvl6HyukfCoHwV3NvRo1ezmOFs8XLgRGviz5DMl9imaI6f1Nfvf0Zyzg2oJHu9cwn1rLdd3+bWcbPXJSlol2ZLC34L6x1p48gm/x8cWA/hfC/fH3kXmdk+VH0wxo+bAUYaIgXBMlkrI34x5D2JN9t1ELlBVH4rO9XW7S/WRAZDo0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/8/26 10:43, Anshuman Khandual wrote: > On 08/07/26 1:31 PM, David Hildenbrand (Arm) wrote: >> On 7/8/26 05:28, 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) >> >> I still think you should add your >> >> Co-developed-by :) > > OK - will add. > >> >>> 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(-) >>> >> >> In general, LGTM (I wrote of it, lol) >> >>> 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 */ >> >> We could reduce the stack space for !__SIZEOF_INT128__, but not sure if worth it. >> >> __print_bad_page_map_pgtable() will currently consume 132 bytes for strings, >> guess that's still tolerable. >> > > That's a good point. Are you looking for something like the following > where stack space can be saved if __SIZEOF_INT128__ is not supported. > > #if defined(__SIZEOF_INT128__) > #define PTVAL_STR_MAX (32 + 1) /* Max 128-bit value in hex + NUL */ > #else > #define PTVAL_STR_MAX (16 + 1) /* Max 64-bit value in hex + NUL */ > #endif Yes, something like that. Again, not sure if we need that right now, but it sure looks logical to try reducing stack usage if easily possible. -- Cheers, David