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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763147902; bh=q1olEHlGpuigXtFzJVBaSoMshU+v/j0ueFTcAUs+I9s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Jy0Sphxk9WR3dz6SBtNjAI3Ag2YV7/GuKr7/FFWOwTamKuZCdqFwcjOXh/hJ3+Ian gArB2pLXfsGjcZhJMAGERlegHCumDDyuUoBmj1JyqZ+TcSSwkqcOWRcSjZEaHruHTr HrsNXqOWkf0E1Ev/PpDXMacfc/DKQHo/itZwh/vqf5IJwgh0wYXAnbIPfEdYnlk/Og UuqFZX3EZTPpv5YL1A2XaeykoteoPNQk+uMRFmWUutc8D8qK9T0JtawgKlAsQ14Fvo 3H2TJ1HaqAsNxl3ZCl+UIskhnYGaee2i1MaTooLgDSAmlPF0YPtnNKeV90KBT10itb baNAz/2G9utJw== Date: Fri, 14 Nov 2025 12:18:17 -0700 From: Nathan Chancellor To: Matthew Wilcox Cc: kernel test robot , "David Hildenbrand (Red Hat)" , llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, Andrew Morton , Linux Memory Management List , linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy Subject: Re: [akpm-mm:mm-unstable 36/283] mm/hugetlb.c:4753:18: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 17179869184 to 0 Message-ID: <20251114191817.GA1089438@ax162> References: <202511141140.LrrRrtIv-lkp@intel.com> <20251114182956.GD2566209@ax162> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 7CDA640018 X-Rspamd-Server: rspam07 X-Stat-Signature: h59ii6e5bp98qm4yytntqay8ommt9s9g X-Rspam-User: X-HE-Tag: 1763147903-125156 X-HE-Meta: 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 2paZCPJv FL2Vj1YJbidgAZqTMDphbdV/AiCL6PlPhB6SwyWm/tM/ky9zJ4b/x+/VxgPyM8FH1dudYvcZBeX5Xhl36UEC9Ow4UsWs7WxTRBu7LDW9HDMr021rt9JslIwD+1efN7MJhZKg1z+eEdHLfznmfKbBndIYKkmNXHA836g3eAyOeelvzQcLjhPaGIdzpzYwFjbM5yTd7eEPpJSA/Fuwaz5hTFFTD5J5pn0EpVuZcIDVmlc0ZXZPueBSFItfrqkOmlnoLq3GoY054bMla5N09iWng7bD9rw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Nov 14, 2025 at 06:54:47PM +0000, Matthew Wilcox wrote: > On Fri, Nov 14, 2025 at 11:29:56AM -0700, Nathan Chancellor wrote: > > > >> mm/util.c:1263:16: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 17179869184 to 0 [-Wconstant-conversion] > > > 1263 | if (ps->idx < MAX_FOLIO_NR_PAGES) { > > > | ^~~~~~~~~~~~~~~~~~ > > > include/linux/mm.h:2104:36: note: expanded from macro 'MAX_FOLIO_NR_PAGES' > > > 2104 | #define MAX_FOLIO_NR_PAGES (1UL << MAX_FOLIO_ORDER) > > > | ^~~~~~~~~~~~~~~ > > > include/linux/mm.h:2095:36: note: expanded from macro 'MAX_FOLIO_ORDER' > > > 2095 | #define MAX_FOLIO_ORDER get_order(SZ_16G) > > > | ~~~~~~~~~ ^~~~~~ > > > include/linux/sizes.h:56:19: note: expanded from macro 'SZ_16G' > > > 56 | #define SZ_16G _AC(0x400000000, ULL) > > > | ^~~~~~~~~~~~~~~~~~~~~ > > Clearly this is a 32-bit build, since otherwise a conversion from > "unsigned long long" to "unsigned long" is a NOP. But 32-bit cannot > support 16GB folios! > > I say this is a bug in powerpc32's config. > > #if !defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) > #define MAX_FOLIO_ORDER MAX_PAGE_ORDER > ... > #else > #define MAX_FOLIO_ORDER PUD_ORDER > > (PUD_ORDER is 16GB, so I think this will be what's being picked up) > > but the only place the mentions ARCH_HAS_GIGANTIC_PAGE is pretty > clearly dependent on 64bit ... > > config PPC_RADIX_MMU > bool "Radix MMU Support" > depends on PPC_BOOK3S_64 > select ARCH_HAS_GIGANTIC_PAGE > > so I'm a bit stuck about how this comes to be. Adding the PPC people > for thoughts. Note that the original report is against mm-unstable and flags https://git.kernel.org/akpm/mm/c/c3f81a41ba6f93693d208edde08ce2b0da21c645 https://lore.kernel.org/20251112145632.508687-1-david@kernel.org/ in mm-hotfixes-unstable as the problematic change. This configuration ends up with $ rg -N 'HAVE_GIGANTIC|HUGETLB|PPC_8xx' .config # CONFIG_CGROUP_HUGETLB is not set CONFIG_PPC_8xx=y CONFIG_HAVE_GIGANTIC_FOLIOS=y CONFIG_ARCH_SUPPORTS_HUGETLBFS=y CONFIG_HUGETLBFS=y CONFIG_HUGETLB_PAGE=y config PPC_8xx bool "Freescale 8xx" select ARCH_SUPPORTS_HUGETLBFS select FSL_SOC select PPC_KUEP select HAVE_ARCH_VMAP_STACK select HUGETLBFS which may indicate a bug in either selecting ARCH_HAS_GIGANTIC_PAGE in this case or the logic of HAVE_GIGANTIC_FOLIOS in that change? Cheers, Nathan