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 B8E682F12A5 for ; Wed, 8 Jul 2026 08:52:34 +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=1783500755; cv=none; b=RdrNh1hXZjYCxPmN6wV3cfZXFfaGtbEeOr7qUy/vTdseyw8fSlbctKoeE0n86tohK1fJ0HAbfUcR0gyp1rvgHs4qzV3Bqi4g2B3TJiVSaEXjqmkZLitFOldgOv38uvUJH9f7EtbRb2PZmo8HYvtGHBrywemGExnEkeBRLo398YQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783500755; c=relaxed/simple; bh=gFzPJ5R5jL7yf+oglcyCOCVFwHYb21NHZVi5uYmJrFU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CE7VSpgfcYzhyP0BvaRSg03n+C2+0DGXoGwpMrhCwrH40WuDaHcFkryS29UgOO04eg8I3NGEq6Rw9kQg44qnCOO6/LmT3uUQYbaQOdEHNl77iReB/EbnxTHO7LCeI5KJRmhxADH4zdxBWNxGXs95cKgW+NjyLEDzNt9mT9gwp88= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IYWfqZFr; 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="IYWfqZFr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 083871F00A3A; Wed, 8 Jul 2026 08:52:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; 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 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 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 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