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=1793306645; b=QC7BUm9XKeHRlQ41XsPweDo/Q8MLYWJCJokVvR8ryysxM8ZNXD7Ks2qHoKdPFjYOII7P p0fGjJvsx2ovF7ecju3I8ezjlFOYJYd3aFg3I4jEW3n5maPtWiOkvf1kmv3Ofol8AoFTt +DieQdOy7+PB6D+8LpuBhE82izPtlW2phxTZdK5kSQ2u1+f/FlIALv9fqGfFLSRYJs1yV NfTzxfw29qkIWh2EYuJh74VMCQx/nNOWVuuC4k8lnwP54bOi/n+b9xyolNAhCPcPKNP7O mrhqdQiWdSXp9GH0lWcPT+4Wm7gpAH/cUDnV56QjVEryocTljlQzJIie29WtTwibN8Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306645; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=PI8EmdBn37j7qc/hvMAGTDVDDo5VBf2eU5QEycECV2k=; b=E00Np4NgV11zgSmHIb+ogzKPqVLl6zMjQl6JIrtbjYG5/eAbs7SFc/b6PJ4eg7fztTqm TiC84aP/vRFqSfIg5lo3QBlYPUqrlK1hBGhkOhLRZBUGqfucZwXfjew8rNjMjK7zukPhx f6XwtjNCcFXeVzRJkroNIRv+ZIKmXHD3Z7O/NJcc66w8lgNcxHubegR0alWgBPqIMIMHY OaF4TC3gQoOygNEpQZmfahTxY9ZhoDAZXYWKDoDF/QZNxbrYc9cEYoX09Hdu34l57vxt1 ZCUHlb/OplgTMsUGUQTypzyXBSB5qBhcru04tMre+ZbjUU7r1FgBdb5hgK107NmwRJw== 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=I3wM2Fp2; 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 72E7B606A31F; Thu, 29 Oct 2026 20:44:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=I3wM2Fp2 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1ABD81F01826; Thu, 29 Oct 2026 20:43:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306645; bh=PI8EmdBn37j7qc/hvMAGTDVDDo5VBf2eU5QEycECV2k=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=I3wM2Fp2M/mnFZOoLQjrOOGcJn2Tv+0zUzVbgWBHluank6O6Jj1/hRTD8bqfwKQr4 zHGg1evLbpkE+EIITtj8IU/8h5sV5/cwswPhYhl58K+pNMq7yafhM/3QJ/6tSZvjtc EIkF69eSqkz5J1NC2rlbPl+flcQ/bjkq88b6bJXNhOBiP8sgZRILnp8rnBww98GwHz WXdmRGcnvgjlqG7d/lH2c1NXRCKkWqDCNw2Js2U532SmcF2gBH4YHMWqG1WEOaK84E XQRunhZ8gsVpvKbm8t04i7F4xsicZijv9ybjklw+5K7P0vn1r3nGM9fxxNtquFNu1P xH52ZIz0oh+VA== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:38 +0100 Subject: [PATCH v2 43/47] mm/huge_memory: split huge PUDs when adjusting VMA boundaries X-Mailing-List: linux-arch@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: 7bit Message-Id: <20261029-fixes_core-v2-43-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3933; i=david@kernel.org; h=from:subject:message-id; bh=QffgpAOB3agwHlZzTMqGo5KOI/hFG36iruKivYKWL2Q=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer+303vND6POzBp0C/l2WzFfevlivUbNg/4TeZ/vCm T3+ZP1b0FHKwiDGwSArpsgSFHzf4OXLdbXVbnzMMHNYmUCGMHBxCsBEZnozMkwLOl5Wk5Bj1Thd SFvk4Twt9r1svrlLZnWGliUJ23L9vMbwV86BzahUqf7TnN3Gc6RW/hTcvvzy1FTBp8v2vL6/5VD ZYz4A X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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 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 f1b3f744c630..6ff3faa200f9 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); } /* -- 2.43.0