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 56C4A420874 for ; Tue, 7 Jul 2026 09:28:49 +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=1783416530; cv=none; b=awq94OHR0cBmAWDTKtP46dqOtmU6dc4fIMlU89FFyxI2dhOzIC8cVfN3IhG9gIQ6Btc7mOrGmB6WR/HUijyrXT7fIgpKdyShd+qvNy4flTOc8UC/DmmpIWFmOw91uJ0/TH7+ETOMB7W41YbWj5QoWuCoT/caqpFJusyuma53V6w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783416530; c=relaxed/simple; bh=wR0HLef+uexVnyW83w27rjFZRdWDEWmv/+/gVg9MHPc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=WqKdG/AZmWZn7NN7UnrhUph6RcfucZ+X9gO/H3WcKCF1QQB0SCxbTHx+fiawVMmAERKOBBaOL8o9wVlr9+sg1J99LLrpywzF4PmW8NAGj1h99WR9F+QULRkOiTqD8LXGvBSajnvcHf/mf4UfUtGectsuRl0WQvYuuZeSSbran7g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KSQTh9/u; 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="KSQTh9/u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 273CD1F000E9; Tue, 7 Jul 2026 09:28:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783416529; bh=XJk7wa5Iey8ZXCCay2oQE5KRjSmBtrQLK5MUIYTrwzw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=KSQTh9/ubHH7JaMb7yuW6lCxLYkWQGOdjjP6EHaXgQ28ARKOM7xhzL867Jtkr3qfn pXe6q9YeT1kkeKEcxTkOXTNLMBpS6JZXcKF151EFyQBCJhJDdsBU5bLje8jmHaFwA7 H77MtRPygRe3w4pLxzuiigxoEwy8932OJm1elVjKgyE4aVdXNBF1RKOrOZ9d3ZA3cF vO66Dp9pZIUtj/k5JNBRPDoT7aPdvT/5mkPIvuPyTTRfk4KUTIapvmovyD5ykMCVdd ARrDtgFvezrTJoxYRfcUzvZm6pp9RMFKVAt6pWmyFbPl+gbZWpfjvT7buGUvqq0JvZ D/P5T0wAE9dpw== Message-ID: Date: Tue, 7 Jul 2026 11:28:45 +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] 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, Andrew Morton , linux-kernel@vger.kernel.org References: <20260707041703.658021-1-anshuman.khandual@arm.com> <5c128db1-7f82-4e2c-b029-5623880ea56d@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/7/26 10:58, Anshuman Khandual wrote: > > > On 07/07/26 12:38 PM, David Hildenbrand (Arm) wrote: >> On 7/7/26 06:17, 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) >> >> You should add a Co-developed-by here :) > > Have not done much changes from your original patch :) Well, you did some :) > >>> --- >> >> [...] >> >>> + >>> +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): { >>> + const u64 *val = entry; >>> + >>> + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) >>> + snprintf(buf, buf_size, "%016llx%016llx", val[0], val[1]); >>> + else >>> + snprintf(buf, buf_size, "%016llx%016llx", val[1], val[0]); >>> + break; >> >> As discussed, can we simplify that by casting to (u128) and then shifting the >> values into place? > > which would be something like the following - had similar > construct in D128 RFC V2 series as well. > > snprintf(buf, buf_size, "%016llx%016llx", > (unsigned long long)*(const u128 *)entry >> 64), > (unsigned long long)*(const u128 *)entry; > > I did think about it but is not the proposed chunk bit cleaner > instead and easier to follow. Do you have concern regarding u64 > pointers into u128 then accessed in chunks ? Regardless don't > have a strong opinion either way. I think any removed endianess dependency is a thing worth considering :) -- Cheers, David