From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F3DD0105F7AE for ; Fri, 13 Mar 2026 14:18:18 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4677E10E36C; Fri, 13 Mar 2026 14:18:18 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="CXn9MAoU"; dkim-atps=neutral Received: from mail-dy1-f171.google.com (mail-dy1-f171.google.com [74.125.82.171]) by gabe.freedesktop.org (Postfix) with ESMTPS id 63B9A10E36C for ; Fri, 13 Mar 2026 14:18:17 +0000 (UTC) Received: by mail-dy1-f171.google.com with SMTP id 5a478bee46e88-2beab594d8eso536924eec.0 for ; Fri, 13 Mar 2026 07:18:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773411497; x=1774016297; darn=lists.freedesktop.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=r1meeHFmJysBuX7/16oB76k0jIo/jgbnm0xUY/2rAoc=; b=CXn9MAoUZyfPcOzLE4fOofYQuVCZSK3nFexwM1nY8bhpWAnRP3hpc6nNU1EiLwzcyh eD1acKc5K8YbT0U833T5C64c1adrAV8mtRdJR5amEO5ejnBBr+suqDViIkWbtPZmMibV 16qVN9Pj2427I9NDAIcLksx3RuWc7JHn3n1RxaN1QTvWCkAdCc35rlZ247tNnNRU8sxe OO4FZoo47/+dX7Wz2f31zrbuthun+lKD+NQaaxehnxP5pQn7bkqcA97JaFnNyevOa3Rm 6Ru2eevXAnqAO4jf/We7hp/0FFjpD45R9Cb+TlstmoI4H1HIZup6ZTvMHoZ9IvSzMv0s 6p8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773411497; x=1774016297; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=r1meeHFmJysBuX7/16oB76k0jIo/jgbnm0xUY/2rAoc=; b=PkwP6EnDuKHXe1wKu7m20v74LFh8yHnCgxJJDxRh1XRvgmTWvo7GAXLy5a7+zKSAHv GCFeqoLsoR6ZYYyhgH/0vpdxmS3FlcWCXOKZ+wfYZ54WUnYTLhPeQgpEMlgc15L8t6t7 7v7Dl4sBwzV1M4mI7lXCpxy78IjpF2agnNMMSnlMn47waUZIiVQz9i1ExWHV54pS8kUI RE9m9enQc+3jeTT99MTYWY5XE4dD3uVnBN8AC8HYdCXpu1a0Y9upTUEgTYTspzCPHZmN IJ+2/0krZ9xbg0VpwCwxBwATa2ZVJPqVp20cjEY3LnyktihaIugPJuPIFVzTY9PqM9/5 ZC0w== X-Gm-Message-State: AOJu0YyhFDB1Oa27uUsj9Jd8Mk8/iKoM4Sby/2tkVZ+jDI5PH3myxrPQ H236X5V6haG5enDLdeM/cLXuQufLkfBJtFKKr5dElD8Kn05yVnQeeMGh X-Gm-Gg: ATEYQzzpgMTqJyO5Wc98tgibbqxKHhIT9itgHcREe/3eKbXBddfjcP3vnzG+sPfpe3v XSc0irDdSgYXhox+gB290doOUVO6z2p8yksyWXyE0zVorBRV4S/qkKsIpWnsFI++yb5cGQ8hwi+ +ikpwDTa/eBloEGWSwZmZ0aHt+S8cy9+piaR9H55YBx2pcwNfpSL1fXYauR1JDWkVyBO1ilmkA3 C6uDDOe19vx++88IgdSB0yX3fS9JvBMeq5h9msDesSVAAhqKR0sw4+xjzJyQndre5llE0p7DR5F RhoHNytov6fErXyWr3hbf/VrY5gauSRyqb1e9fOwGz5Q3pnEsO72pPZl4YMhKZ+cdsCrvY6G3fk bKIzvG+8c0c5NAJdOfTppiYbj9/Im4wW72QkJ6MkVf1VSYasi59Zb4YizdVSDUXiRyIeUAY2VXu DgZWPExXrDHCCgMCe5Wd5m+qRepjo4qpDuGA9WWyw74NoGdCzkTJ7bITA= X-Received: by 2002:a05:7301:3806:b0:2ba:a712:51e3 with SMTP id 5a478bee46e88-2bea558f2dcmr1668586eec.21.1773411496218; Fri, 13 Mar 2026 07:18:16 -0700 (PDT) Received: from fedora ([177.73.136.69]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2beab526d61sm3023095eec.17.2026.03.13.07.18.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 07:18:15 -0700 (PDT) From: Pedro Demarchi Gomes To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Boris Brezillon , Loic Molinari Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Pedro Demarchi Gomes Subject: [PATCH v2] drm/shmem-helper: Fix Map huge page mapping in fault handler Date: Fri, 13 Mar 2026 11:17:19 -0300 Message-ID: <20260313141719.3949700-1-pedrodemargomes@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" When running ./tools/testing/selftests/mm/split_huge_page_test multiple times with /sys/kernel/mm/transparent_hugepage/shmem_enabled and /sys/kernel/mm/transparent_hugepage/enabled set as always the following BUG occurs: [ 232.728858] ------------[ cut here ]------------ [ 232.729458] kernel BUG at mm/memory.c:2276! [ 232.729726] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI [ 232.730217] CPU: 19 UID: 60578 PID: 1497 Comm: llvmpipe-9 Not tainted 7.0.0-rc1mm-new+ #19 PREEMPT(lazy) [ 232.730855] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-9.fc43 06/10/2025 [ 232.731360] RIP: 0010:walk_to_pmd+0x29e/0x3c0 [ 232.731569] Code: d8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 48 89 ea 48 89 de 4c 89 f7 e8 ae 85 ff ff 85 c0 0f 84 1f fe ff ff 31 db eb d0 <0f> 0b 48 89 ea 48 89 de 4c 89 f7 e8 92 8b ff ff 85 c0 75 e8 48 b8 [ 232.732614] RSP: 0000:ffff8881aa6ff9a8 EFLAGS: 00010282 [ 232.732991] RAX: 8000000142e002e7 RBX: ffff8881433cae10 RCX: dffffc0000000000 [ 232.733362] RDX: 0000000000000000 RSI: 00007fb47840b000 RDI: 8000000142e002e7 [ 232.733801] RBP: 00007fb47840b000 R08: 0000000000000000 R09: 1ffff110354dff46 [ 232.734168] R10: fffffbfff0cb921d R11: 00000000910da5ce R12: 1ffffffff0c1fcdd [ 232.734459] R13: 1ffffffff0c23f36 R14: ffff888171628040 R15: 0000000000000000 [ 232.734861] FS: 00007fb4907f86c0(0000) GS:ffff888791f2c000(0000) knlGS:0000000000000000 [ 232.735265] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 232.735548] CR2: 00007fb47840be00 CR3: 000000015e6dc000 CR4: 00000000000006f0 [ 232.736031] Call Trace: [ 232.736273] [ 232.736500] get_locked_pte+0x1f/0xa0 [ 232.736878] insert_pfn+0x9f/0x350 [ 232.737190] ? __pfx_pat_pagerange_is_ram+0x10/0x10 [ 232.737614] ? __pfx_insert_pfn+0x10/0x10 [ 232.737990] ? __pfx_css_rstat_updated+0x10/0x10 [ 232.738281] ? __pfx_pfn_modify_allowed+0x10/0x10 [ 232.738552] ? lookup_memtype+0x62/0x180 [ 232.738761] vmf_insert_pfn_prot+0x14b/0x340 [ 232.739012] ? __pfx_vmf_insert_pfn_prot+0x10/0x10 [ 232.739247] ? __pfx___might_resched+0x10/0x10 [ 232.739475] drm_gem_shmem_fault.cold+0x18/0x39 [ 232.739677] ? rcu_read_unlock+0x20/0x70 [ 232.739882] __do_fault+0x251/0x7b0 [ 232.740028] do_fault+0x6e1/0xc00 [ 232.740167] ? __lock_acquire+0x590/0xc40 [ 232.740335] handle_pte_fault+0x439/0x760 [ 232.740498] ? mtree_range_walk+0x252/0xae0 [ 232.740669] ? __pfx_handle_pte_fault+0x10/0x10 [ 232.740899] __handle_mm_fault+0xa02/0xf30 [ 232.741066] ? __pfx___handle_mm_fault+0x10/0x10 [ 232.741255] ? find_vma+0xa1/0x120 [ 232.741403] handle_mm_fault+0x2bf/0x8f0 [ 232.741564] do_user_addr_fault+0x2d3/0xed0 [ 232.741736] ? trace_page_fault_user+0x1bf/0x240 [ 232.741969] exc_page_fault+0x87/0x120 [ 232.742124] asm_exc_page_fault+0x26/0x30 [ 232.742288] RIP: 0033:0x7fb4d73ed546 [ 232.742441] Code: 66 41 0f 6f fb 66 44 0f 6d dc 66 44 0f 6f c6 66 41 0f 6d f1 66 0f 6c fc 66 45 0f 6c c1 66 44 0f 6f c9 66 0f 6d ca 66 0f db f0 <66> 0f df 04 08 66 44 0f 6c ca 66 45 0f db c2 66 44 0f df 10 66 44 [ 232.743193] RSP: 002b:00007fb4907f68a0 EFLAGS: 00010206 [ 232.743565] RAX: 00007fb47840aa00 RBX: 00007fb4d73ec070 RCX: 0000000000001400 [ 232.743871] RDX: 0000000000002800 RSI: 0000000000003c00 RDI: 0000000000000001 [ 232.744150] RBP: 0000000000000004 R08: 0000000000001400 R09: 00007fb4d73ec060 [ 232.744433] R10: 000055f0261a4288 R11: 00007fb4c013da40 R12: 0000000000000008 [ 232.744712] R13: 0000000000000000 R14: 4332322132212110 R15: 0000000000000004 [ 232.746616] [ 232.746711] Modules linked in: nft_nat nft_masq veth bridge stp llc snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore overlay rfkill nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables qrtr ppdev 9pnet_virtio 9pnet parport_pc i2c_piix4 netfs pcspkr parport i2c_smbus joydev sunrpc vfat fat loop dm_multipath nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport zram lz4hc_compress vmw_vmci lz4_compress vsock e1000 bochs serio_raw ata_generic pata_acpi scsi_dh_rdac scsi_dh_emc scsi_dh_alua i2c_dev fuse qemu_fw_cfg [ 232.749308] ---[ end trace 0000000000000000 ]--- [ 232.749507] RIP: 0010:walk_to_pmd+0x29e/0x3c0 [ 232.749692] Code: d8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 48 89 ea 48 89 de 4c 89 f7 e8 ae 85 ff ff 85 c0 0f 84 1f fe ff ff 31 db eb d0 <0f> 0b 48 89 ea 48 89 de 4c 89 f7 e8 92 8b ff ff 85 c0 75 e8 48 b8 [ 232.750428] RSP: 0000:ffff8881aa6ff9a8 EFLAGS: 00010282 [ 232.750645] RAX: 8000000142e002e7 RBX: ffff8881433cae10 RCX: dffffc0000000000 [ 232.750954] RDX: 0000000000000000 RSI: 00007fb47840b000 RDI: 8000000142e002e7 [ 232.751232] RBP: 00007fb47840b000 R08: 0000000000000000 R09: 1ffff110354dff46 [ 232.751514] R10: fffffbfff0cb921d R11: 00000000910da5ce R12: 1ffffffff0c1fcdd [ 232.751837] R13: 1ffffffff0c23f36 R14: ffff888171628040 R15: 0000000000000000 [ 232.752124] FS: 00007fb4907f86c0(0000) GS:ffff888791f2c000(0000) knlGS:0000000000000000 [ 232.752441] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 232.752674] CR2: 00007fb47840be00 CR3: 000000015e6dc000 CR4: 00000000000006f0 [ 232.752983] Kernel panic - not syncing: Fatal exception [ 232.753510] Kernel Offset: disabled [ 232.754643] ---[ end Kernel panic - not syncing: Fatal exception ]--- This happens when two concurrent page faults occur within the same PMD range. One fault installs a PMD mapping through vmf_insert_pfn_pmd(), while the other attempts to install a PTE mapping via vmf_insert_pfn(). The bug is triggered because a pmd_trans_huge is not expected when walking the page table inside vmf_insert_pfn. Avoid this race by adding a huge_fault callback to drm_gem_shmem_vm_ops so that PMD-sized mappings are handled through the appropriate huge page fault path. Fixes: 211b9a39f261 ("drm/shmem-helper: Map huge pages in fault handler") Signed-off-by: Pedro Demarchi Gomes --- Changes in v2: - Keep the #ifdef unindented - Create drm_gem_shmem_any_fault to handle faults of any order and use drm_gem_shmem_[huge_]fault() as wrappers --- drivers/gpu/drm/drm_gem_shmem_helper.c | 67 +++++++++++++++----------- 1 file changed, 39 insertions(+), 28 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 7b5a49935ae4..fb8b74ac3057 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -550,36 +550,19 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev, } EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create); -static bool drm_gem_shmem_try_map_pmd(struct vm_fault *vmf, unsigned long addr, - struct page *page) -{ -#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP - unsigned long pfn = page_to_pfn(page); - unsigned long paddr = pfn << PAGE_SHIFT; - bool aligned = (addr & ~PMD_MASK) == (paddr & ~PMD_MASK); - - if (aligned && - pmd_none(*vmf->pmd) && - folio_test_pmd_mappable(page_folio(page))) { - pfn &= PMD_MASK >> PAGE_SHIFT; - if (vmf_insert_pfn_pmd(vmf, pfn, false) == VM_FAULT_NOPAGE) - return true; - } -#endif - - return false; -} - -static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) +static vm_fault_t drm_gem_shmem_any_fault(struct vm_fault *vmf, + unsigned int order) { struct vm_area_struct *vma = vmf->vma; struct drm_gem_object *obj = vma->vm_private_data; struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); loff_t num_pages = obj->size >> PAGE_SHIFT; - vm_fault_t ret; + vm_fault_t ret = VM_FAULT_FALLBACK; struct page **pages = shmem->pages; pgoff_t page_offset; unsigned long pfn; + unsigned long paddr; + bool aligned; /* Offset to faulty address in the VMA. */ page_offset = vmf->pgoff - vma->vm_pgoff; @@ -593,13 +576,24 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) goto out; } - if (drm_gem_shmem_try_map_pmd(vmf, vmf->address, pages[page_offset])) { - ret = VM_FAULT_NOPAGE; - goto out; - } - pfn = page_to_pfn(pages[page_offset]); - ret = vmf_insert_pfn(vma, vmf->address, pfn); + switch (order) { + case 0: + ret = vmf_insert_pfn(vma, vmf->address, pfn); + break; +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP + case PMD_ORDER: + paddr = pfn << PAGE_SHIFT; + aligned = (vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK); + + if (aligned && + folio_test_pmd_mappable(page_folio(pages[page_offset]))) { + pfn &= PMD_MASK >> PAGE_SHIFT; + ret = vmf_insert_pfn_pmd(vmf, pfn, false); + } + break; +#endif + } out: dma_resv_unlock(shmem->base.resv); @@ -607,6 +601,20 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) return ret; } +static vm_fault_t drm_gem_shmem_huge_fault(struct vm_fault *vmf, + unsigned int order) +{ + if (order != PMD_ORDER) + return VM_FAULT_FALLBACK; + + return drm_gem_shmem_any_fault(vmf, order); +} + +static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) +{ + return drm_gem_shmem_any_fault(vmf, 0); +} + static void drm_gem_shmem_vm_open(struct vm_area_struct *vma) { struct drm_gem_object *obj = vma->vm_private_data; @@ -643,6 +651,9 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma) const struct vm_operations_struct drm_gem_shmem_vm_ops = { .fault = drm_gem_shmem_fault, +#ifdef CONFIG_ARCH_SUPPORTS_HUGE_PFNMAP + .huge_fault = drm_gem_shmem_huge_fault, +#endif .open = drm_gem_shmem_vm_open, .close = drm_gem_shmem_vm_close, }; -- 2.53.0