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[80.187.83.189]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fa9d62890sm68237045e9.14.2025.10.09.00.22.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Oct 2025 00:22:19 -0700 (PDT) Message-ID: Date: Thu, 9 Oct 2025 09:22:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: (bisected) [PATCH v2 08/37] mm/hugetlb: check for unreasonable folio sizes when registering hstate To: Christophe Leroy , linux-kernel@vger.kernel.org Cc: Zi Yan , Lorenzo Stoakes , "Liam R. Howlett" , Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, "linuxppc-dev@lists.ozlabs.org" References: <20250901150359.867252-1-david@redhat.com> <20250901150359.867252-9-david@redhat.com> <3e043453-3f27-48ad-b987-cc39f523060a@csgroup.eu> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" On 09.10.25 09:14, Christophe Leroy wrote: > Hi David, > > Le 01/09/2025 à 17:03, David Hildenbrand a écrit : >> Let's check that no hstate that corresponds to an unreasonable folio size >> is registered by an architecture. If we were to succeed registering, we >> could later try allocating an unsupported gigantic folio size. >> >> Further, let's add a BUILD_BUG_ON() for checking that HUGETLB_PAGE_ORDER >> is sane at build time. As HUGETLB_PAGE_ORDER is dynamic on powerpc, we have >> to use a BUILD_BUG_ON_INVALID() to make it compile. >> >> No existing kernel configuration should be able to trigger this check: >> either SPARSEMEM without SPARSEMEM_VMEMMAP cannot be configured or >> gigantic folios will not exceed a memory section (the case on sparse). >> >> Reviewed-by: Zi Yan >> Reviewed-by: Lorenzo Stoakes >> Reviewed-by: Liam R. Howlett >> Signed-off-by: David Hildenbrand > > I get following warning on powerpc with linus tree, bisected to commit > 7b4f21f5e038 ("mm/hugetlb: check for unreasonable folio sizes when > registering hstate") Do you have the kernel config around? Is it 32bit? That would be helpful. [...] >> --- >> mm/hugetlb.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 1e777cc51ad04..d3542e92a712e 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -4657,6 +4657,7 @@ static int __init hugetlb_init(void) >> >> BUILD_BUG_ON(sizeof_field(struct page, private) * BITS_PER_BYTE < >> __NR_HPAGEFLAGS); >> + BUILD_BUG_ON_INVALID(HUGETLB_PAGE_ORDER > MAX_FOLIO_ORDER); >> >> if (!hugepages_supported()) { >> if (hugetlb_max_hstate || default_hstate_max_huge_pages) >> @@ -4740,6 +4741,7 @@ void __init hugetlb_add_hstate(unsigned int order) >> } >> BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE); >> BUG_ON(order < order_base_2(__NR_USED_SUBPAGE)); >> + WARN_ON(order > MAX_FOLIO_ORDER); >> h = &hstates[hugetlb_max_hstate++]; >> __mutex_init(&h->resize_lock, "resize mutex", &h->resize_key); >> h->order = order; We end up registering hugetlb folios that are bigger than MAX_FOLIO_ORDER. So we have to figure out how a config can trigger that (and if we have to support that). -- Cheers David / dhildenb