From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B5D0D44C63 for ; Mon, 12 May 2025 18:55:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747076131; cv=none; b=KoGyqcYP9mx4VrlSBLgpEppChHsuXSJ2dQdvvUYIW/kYCiYifmkovs3rDkY9JO3V99waYZ0GCZzD1IWbFyA7t8nodZLEYSzzlBoXOD1LqETNJ7aGin9QPkmFjv3uPwqxOT9N7LoxG+fgDxZRtY1hSrDsa3HcCEqcnInhxSJI22U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747076131; c=relaxed/simple; bh=M6ayjQd3gWz51QUvPEksazFGawUZNndcRZ17U3rlaY8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=oKlTnOmuFvCmepRMXARAVPI+Qt8Ckdq2B1hhsxmOry7n3JGmz/kAoL69WP1hiYNlaiL0Fsq5cx8gL4zjkTC63ZHhBuMU0yng2/GZ/zNiJ1VT9aqNT+1JqRlbTMBBk5h6aqtxM8b0f33VQsayaSI0xfpWVBBG2gRrTA0HfjgpqfE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98462C4CEE7; Mon, 12 May 2025 18:55:28 +0000 (UTC) Date: Mon, 12 May 2025 19:55:25 +0100 From: Catalin Marinas To: Ryan Roberts Cc: Will Deacon , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , David Hildenbrand , "Matthew Wilcox (Oracle)" , Mark Rutland , Anshuman Khandual , Alexandre Ghiti , Kevin Brodsky , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64/mm: Permit lazy_mmu_mode to be nested Message-ID: References: <20250512150333.5589-1-ryan.roberts@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250512150333.5589-1-ryan.roberts@arm.com> On Mon, May 12, 2025 at 04:03:31PM +0100, Ryan Roberts wrote: > lazy_mmu_mode is not supposed to permit nesting. But in practice this > does happen with CONFIG_DEBUG_PAGEALLOC, where a page allocation inside > a lazy_mmu_mode section (such as zap_pte_range()) will change > permissions on the linear map with apply_to_page_range(), which > re-enters lazy_mmu_mode (see stack trace below). > > The warning checking that nesting was not happening was previously being > triggered due to this. So let's relax by removing the warning and > tolerate nesting in the arm64 implementation. The first (inner) call to > arch_leave_lazy_mmu_mode() will flush and clear the flag such that the > remainder of the work in the outer nest behaves as if outside of lazy > mmu mode. This is safe and keeps tracking simple. > > Code review suggests powerpc deals with this issue in the same way. > > ------------[ cut here ]------------ > WARNING: CPU: 6 PID: 1 at arch/arm64/include/asm/pgtable.h:89 __apply_to_page_range+0x85c/0x9f8 > Modules linked in: ip_tables x_tables ipv6 > CPU: 6 UID: 0 PID: 1 Comm: systemd Not tainted 6.15.0-rc5-00075-g676795fe9cf6 #1 PREEMPT > Hardware name: QEMU KVM Virtual Machine, BIOS 2024.08-4 10/25/2024 > pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : __apply_to_page_range+0x85c/0x9f8 > lr : __apply_to_page_range+0x2b4/0x9f8 > sp : ffff80008009b3c0 > x29: ffff80008009b460 x28: ffff0000c43a3000 x27: ffff0001ff62b108 > x26: ffff0000c43a4000 x25: 0000000000000001 x24: 0010000000000001 > x23: ffffbf24c9c209c0 x22: ffff80008009b4d0 x21: ffffbf24c74a3b20 > x20: ffff0000c43a3000 x19: ffff0001ff609d18 x18: 0000000000000001 > x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000003 > x14: 0000000000000028 x13: ffffbf24c97c1000 x12: ffff0000c43a3fff > x11: ffffbf24cacc9a70 x10: ffff0000c43a3fff x9 : ffff0001fffff018 > x8 : 0000000000000012 x7 : ffff0000c43a4000 x6 : ffff0000c43a4000 > x5 : ffffbf24c9c209c0 x4 : ffff0000c43a3fff x3 : ffff0001ff609000 > x2 : 0000000000000d18 x1 : ffff0000c03e8000 x0 : 0000000080000000 > Call trace: > __apply_to_page_range+0x85c/0x9f8 (P) > apply_to_page_range+0x14/0x20 > set_memory_valid+0x5c/0xd8 > __kernel_map_pages+0x84/0xc0 > get_page_from_freelist+0x1110/0x1340 > __alloc_frozen_pages_noprof+0x114/0x1178 > alloc_pages_mpol+0xb8/0x1d0 > alloc_frozen_pages_noprof+0x48/0xc0 > alloc_pages_noprof+0x10/0x60 > get_free_pages_noprof+0x14/0x90 > __tlb_remove_folio_pages_size.isra.0+0xe4/0x140 > __tlb_remove_folio_pages+0x10/0x20 > unmap_page_range+0xa1c/0x14c0 > unmap_single_vma.isra.0+0x48/0x90 > unmap_vmas+0xe0/0x200 > vms_clear_ptes+0xf4/0x140 > vms_complete_munmap_vmas+0x7c/0x208 > do_vmi_align_munmap+0x180/0x1a8 > do_vmi_munmap+0xac/0x188 > __vm_munmap+0xe0/0x1e0 > __arm64_sys_munmap+0x20/0x38 > invoke_syscall+0x48/0x104 > el0_svc_common.constprop.0+0x40/0xe0 > do_el0_svc+0x1c/0x28 > el0_svc+0x4c/0x16c > el0t_64_sync_handler+0x10c/0x140 > el0t_64_sync+0x198/0x19c > irq event stamp: 281312 > hardirqs last enabled at (281311): [] bad_range+0x164/0x1c0 > hardirqs last disabled at (281312): [] el1_dbg+0x24/0x98 > softirqs last enabled at (281054): [] handle_softirqs+0x4cc/0x518 > softirqs last disabled at (281019): [] __do_softirq+0x14/0x20 > ---[ end trace 0000000000000000 ]--- > > Fixes: 5fdd05efa1cd ("arm64/mm: Batch barriers when updating kernel mappings") > Reported-by: Catalin Marinas > Closes: https://lore.kernel.org/linux-arm-kernel/aCH0TLRQslXHin5Q@arm.com/ > Signed-off-by: Ryan Roberts Thanks. This works, no more warnings. The comment looks fine. Reviewed-by: Catalin Marinas