From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794272970; b=yuN0fumo+AY16za5rR3vuFM1NLuOxT2S03HV0q9Mz0aFGi9qqnilrfKlw18RkRwShq8y LzEfhYA585FIG259N440JuLFLQBslbqg5ru50+O3JQIx9OfGvrRBdSDRGDGKyQVhvCQ9B T7ZpEHLapL9B01vuzEjYquDxIpkKYPkrFcOCg9kBLLr4tEVCuubICGjfzGz7by7E9a12o qIWNIuBsZ6r1dntKDpAoCQTDAImfBPq1FeeDPrwaB0MHx3uCgU+MUZyS86i0b/oO7i96k JUVsV3WchBQk9HyBymo68O4I59mwNh3CqCOF8ooiQdZT0Pb9dWkEYp1O/ULWYebeS1A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794272970; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=R3w9pbFmXk4U/1P2NDDd6Igr3BYs7y1NecncpK2dlMY=; b=xtCPXsHZwRfTLQW3eWMnOfkw2oX736b54mbNxMDCgObh9cRpiWyo0hoocdpxEW2K687O NopZZFhIB24lGCLJDOQppITAOiTAezWfgaWDejlThsz9aPBXZN+29ibm+ZtASfWJqMJmA GtvMTLYycfnKaK7bcQs4fbRZfzLGmJovRtfjyGHn5smbL+BnaD9xHlCfHC/ISGMvRLGYe XoCiZoWFq7o/zMb31TUTKLCaLkxn2sSBeEIPVtywWRFy2xKxQkOvvkViLjrEt2EVhO7xi 1eKVJQrE8hgzPJq4qUZLaSLw4MYh93BhyQcOPahT8qM92ODkll2zxh9CVC/jYKvUovQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DVCNURjT; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9FA89606A31C for ; Tue, 10 Nov 2026 01:09:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DVCNURjT Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3D071F0089F; Tue, 10 Nov 2026 01:09:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794272970; bh=R3w9pbFmXk4U/1P2NDDd6Igr3BYs7y1NecncpK2dlMY=; h=From:To:Cc:Subject:Date; b=DVCNURjTRGakg3+SSJ8tV9Ymtm69ljlOGjS36o9J3evYKjgzc6obSFcr3N5czwZns rAJEspHv5K6APcn0dFHRfymlPHJHvkERrjxrt43i+IC/WdMtbgpQRcB/UvdE8sDMuI lB8rRLLnbPTihqIMQ5D//UlglmNLXRUSvQQzXrk85ttocNmrsrB9YOS8wM1mC7eeVY o1iPpiq4qnW4x52YUC/lAbhwidk9fDBlxVt6SEV0TgHWg0UWnM957iL2JoFVZnFtqZ te66Rp4t6GEhovEBkLkIe0eBAlbjc4qsRH4n6HYO2qyUdMKIqBmBavsXQmaDJ5+mS4 ox9x9S/rZfdCA== From: Sasha Levin To: david@kernel.org, usama.anjum@arm.com, kas@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/huge_memory: split huge PUDs when adjusting VMA boundaries" failed to apply to 6.12-stable tree Date: Mon, 9 Nov 2026 20:09:28 -0500 Message-ID: <20261109200928-failed-6.12-23e570927421@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 23e570927421d569fdc510d5f3f29542a43eeda5 # git commit -s git send-email --to '' --in-reply-to '20261109200928-failed-6.12-23e570927421@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 23e570927421d569fdc510d5f3f29542a43eeda5 Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:40:12 +0100 Subject: [PATCH] mm/huge_memory: split huge PUDs when adjusting VMA boundaries PFN mappings such as VFIO PCI BAR mappings can use PUD leaves while allowing VMA splits at page granularity. However, vma_adjust_trans_huge() only handles PMDs. After faulting a writable PUD-sized VFIO BAR mapping, changing its first page to read-only with mprotect() makes the PMD walk treat the PUD leaf as a PMD table. Applying MADV_DONTFORK to the first PMD-sized chunk leaves the PUD spanning two VMAs: the PMD-aligned boundary skips splitting. Walk the page tables once at each adjusted boundary and split a huge PUD or PMD leaf as needed. Handle PUD leaves even when the boundary is PMD-aligned. Fixes: f9e54c3a2f5b7 ("vfio/pci: implement huge_fault support") Cc: stable@vger.kernel.org Tested-by: Muhammad Usama Anjum Reviewed-by: Kiryl Shutsemau (Meta) Link: https://patch.msgid.link/20261031-fixes_core-v3-43-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) --- mm/huge_memory.c | 70 +++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 60 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f10a199548d8f..7de94775a3598 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3504,16 +3504,66 @@ void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, __split_huge_pmd(vma, pmd, address, freeze); } -static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address) +static bool pud_split_required(const struct vm_area_struct *vma, + unsigned long address) { + if (!IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)) + return false; + if (IS_ALIGNED(address, HPAGE_PUD_SIZE)) + return false; /* - * If the new address isn't hpage aligned and it could previously - * contain an hugepage: check if we need to split an huge pmd. + * Only selected VMAs support mapping PUDs for now. Lift the + * restriction once this changes. */ - if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) && - range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE), - ALIGN(address, HPAGE_PMD_SIZE))) - split_huge_pmd_address(vma, address, false); + if (!vma_is_dax(vma) && !vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT)) + return false; + return range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PUD_SIZE), + ALIGN(address, HPAGE_PUD_SIZE)); +} + +static bool pmd_split_required(const struct vm_area_struct *vma, + unsigned long address) +{ + if (IS_ALIGNED(address, HPAGE_PMD_SIZE)) + return false; + + return range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE), + ALIGN(address, HPAGE_PMD_SIZE)); +} + +static void split_huge_leaf(struct vm_area_struct *vma, + unsigned long address) +{ + const bool split_pud = pud_split_required(vma, address); + const bool split_pmd = pmd_split_required(vma, address); + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + + /* + * mmap, VMA and rmap write locks protect the walk; the split helpers + * take the page table locks. + */ + if (!split_pud && !split_pmd) + return; + + pgd = pgd_offset(vma->vm_mm, address); + if (!pgd_present(*pgd)) + return; + + p4d = p4d_offset(pgd, address); + if (!p4d_present(*p4d)) + return; + + pud = pud_offset(p4d, address); + if (pud_leaf(*pud)) + __split_huge_pud(vma, pud, address); + if (!split_pmd || !pud_present(*pud)) + return; + + pmd = pmd_offset(pud, address); + __split_huge_pmd(vma, pmd, address, false); } void vma_adjust_trans_huge(struct vm_area_struct *vma, @@ -3522,14 +3572,14 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, struct vm_area_struct *next) { /* Check if we need to split start first. */ - split_huge_pmd_if_needed(vma, start); + split_huge_leaf(vma, start); /* Check if we need to split end next. */ - split_huge_pmd_if_needed(vma, end); + split_huge_leaf(vma, end); /* If we're incrementing next->vm_start, we might need to split it. */ if (next) - split_huge_pmd_if_needed(next, end); + split_huge_leaf(next, end); } /* -- 2.53.0