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=1794590757; b=Q0GoE3ar3FNhOw8I/Y48KgSuANHMWLy0aHGisbiXzmIxOZJh5EuTiq8mlDkvKXqEeMMl adXJ2077D72c6478G+3JNZp/GG2HpUXPYOz0BvEKwae10hbukdp+NYGqJZ/i4HWTWtrg5 dFcM0MwRv1/mSMdiDhtJ0wwIiX39HKirF8+HCy1AE8GKXTdpKyBCamBrkxjJ4G/BdUiDh aFrd9uFuRusLCPpuTriYfhRHoIgS/VDy5VMK6va0cwde0Fo/yicLwuwkotAp99sSo8Iwy sgrqEl08krSzQTmKdGCh3s/4rIRQbguHq8/dPfH4GK00xiBUOiGfhNtSb5ff+8LzzMA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590757; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=FOo5Eh2q/GV3gk4RleaAZDwFBDRyJQnXrUinhWktmCU=; b=F2dtdFQs73HWDvoXHOE+9LUqGoiKqEbyi/R66DOXvAYdTjoAXfK4PRqMj6Ipxrk2jPfe y8IqUoqWKNyZrKGNE7aH2hamBVPh3Eb3cKfnNAB31n52qh/LQ3vv6yP1gJXPvjk8JHmT6 kGCJ8BofajFJTdf7SRt3DjPNZZSyMGq2WmKJuQPI7cUNaTOdh6syqHnw8rOgEzj8eP4Fz E8EWYaMFbgd+qIFagp/A6IkSXw9lw8COw3NtD3gSVv9nzLfOrSunqn8p0C2ViC/jSENE2 qtB7PjtWwCNhkEmnH1FEYQJX9hf/vQt58fOIBHOsxWXME6ZQSsEgUnUL7K2+q3pHWjw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=LmXspyXI; 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 817CF607C34D; Fri, 13 Nov 2026 17:25:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=LmXspyXI Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2715B1F000C4; Fri, 13 Nov 2026 17:25:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590757; bh=FOo5Eh2q/GV3gk4RleaAZDwFBDRyJQnXrUinhWktmCU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LmXspyXIa1merq+KKaDtTIDINC0BnFjKXH+F6CBdEKO9tBiG4Uq7INZZN251auSq6 QQn2deWpN9iGLC2ZVcPmXw4nLgUYPpCksNMD+g3hT10K+XikmUvpSkOLLTCaU6f1D3 b/p/0xWbLfv1Yb5eYnSGUNyM1IFILturarEi/ruE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Muhammad Usama Anjum , "Kiryl Shutsemau (Meta)" , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.18 658/686] mm/huge_memory: split huge PUDs when adjusting VMA boundaries Date: Fri, 13 Nov 2026 10:53:11 -0500 Message-ID: <20261113153844.025399328@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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: Replaced vma_test_any() with a direct vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP) test. ] 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 78fecc3ad5700..24f5887eb48ee 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3210,16 +3210,66 @@ 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->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(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, @@ -3228,14 +3278,14 @@ 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); } static void unmap_folio(struct folio *folio) -- 2.53.0