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=1794416868; b=xA4qr9VKmfv7ULGkfpoQbz5qhCf+tRWE2ejarsB1byC3N0436DbMBckTOc4y02K35F15 59LUEyUHfSB36h5V0X428/vtEvxKmnVIH7iNWO3MHn4CbbvZlSB8lYr7RyOM9GHmpM/A+ qxkTfZDev1CSDBOJgqSGC1waAMrxcZf99imMHMq0GCIGdKtPpgDlgezZXXRRdCQSZeV8y l7Jmtoz+UJo/sntMd1FyJMTWb5W1TDG1kAez7CGFze2H//XBDbuZqeA9tIq9CMlapasDn LtIjPRlDW+aDzhSbiQ2WjYab2o2CDOYMkUuMYA8E9WVMfUuLXSVZgexBTZJyK+xFPJw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794416868; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=SkYCjPlJgjChGkaUGiOIodXlewqSkVNXvO6WIToyEvo=; b=ujY3v0xBSx82mxhbxL+n8bnAk+KSTRFN+OY6b0b9gbIiVxuygXJK6LTquqg2brO0QZyd CUs0dIjxGW7DkSLrCRl28/ADilEAeI7jbfxL5uI6c/fZhSsrrUdFTY4qur3/SButrHjz+ FknqwfcU/yj5irMR9xLAguT+4kwuav69q1cjRjdAyfJw9zJ+l3OhCFgIQWy4OWy7OYJCK /G8JRlSYWOLVEtFHnG7Z/aPmlEVDo32cMgq886L2vO+qjOY+wxyNIcp83U7Ty8QQmffKw AHYqQwVS2CzO2bHdC4aE6iVx0iKVJte4JHhgez63f6WLJUh3PrgXHs+Xy+ql6dpTyxw== 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="BCacnUD/"; 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 297FA606A324 for ; Wed, 11 Nov 2026 17:07:47 +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=BCacnUD/ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37ABC1F00A06; Wed, 11 Nov 2026 17:07:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794416867; bh=SkYCjPlJgjChGkaUGiOIodXlewqSkVNXvO6WIToyEvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BCacnUD/GhtvAS8YD1E92w3SMnVgUGOOf+CjbyMd+E/0BRyquIbc4KZKAz3SejHw4 A2aVDU1RSqSjH5am5M89hA63s13lzzKeULQ/JUn2rPTmuCs1o/nKvGqDhLEEAfzUVs l+M6gnIiAIYlFrQEmLYhVSW1XY4x2gmY6/cNgv1Qi+xUhFtNR3F9b2JTJunDQjRfWb MKDChQKstnBuBlonlFNdjU9ung4Kx663M+XJHE4PfTvS3d+tyIe9X8xF0sxmG5dfpA l+w6LMSYs60rWti0lzKbE3nVIFBIYoaDeXTwMJCjhmMGG72p7VHU2yUhs1c1bQxxC9 n7LfhBbEdMUFQ== From: Sasha Levin To: stable@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Muhammad Usama Anjum , "Kiryl Shutsemau (Meta)" , Sasha Levin Subject: [PATCH 6.12.y] mm/huge_memory: split huge PUDs when adjusting VMA boundaries Date: Wed, 11 Nov 2026 12:07:46 -0500 Message-ID: <20261111170708.3419248-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109200928-failed-6.12-23e570927421@kernel.org> References: <20261109200928-failed-6.12-23e570927421@kernel.org> 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-Transfer-Encoding: 8bit From: "David Hildenbrand (Arm)" [ Upstream commit 23e570927421d569fdc510d5f3f29542a43eeda5 ] 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) [ sashal: adapted huge-page splitting helpers to the older VMA and page-table interfaces ] Signed-off-by: Sasha Levin --- 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 d175e93988a92..ce4d17871ff43 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2988,16 +2988,66 @@ void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, __split_huge_pmd(vma, pmd, address, freeze, folio); } -static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address) +static bool pud_split_required(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, NULL); + if (!vma_is_dax(vma) && !(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))) + return false; + return range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PUD_SIZE), + ALIGN(address, HPAGE_PUD_SIZE)); +} + +static bool pmd_split_required(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, NULL); } void vma_adjust_trans_huge(struct vm_area_struct *vma, @@ -3006,10 +3056,10 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, long adjust_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 also updating the next vma vm_start, @@ -3019,7 +3069,7 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end); unsigned long nstart = next->vm_start; nstart += adjust_next; - split_huge_pmd_if_needed(next, nstart); + split_huge_leaf(next, nstart); } } -- 2.53.0