From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 DBA3B390229; Tue, 6 Oct 2026 23:44:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791330293; cv=none; b=gMLHZzu+P2UHIkj1NzRuIarQDaY5Vh5TyiFXKfXNuBMwYygtVeZD3WX/6MH/adYT8f/dFaUWFoEkBtTkG0mJo5785k2rvXAM09LcKnEj1DaAmFX38s0XOyTxrbK5z10STmDJa7Ly9pD/ZtjFhktX3d2X3PR4SXozF0uGbkwKMG0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791330293; c=relaxed/simple; bh=lA5dc71kgN9osN83Izs74lDtLqDEeBqDqX4lvAv9E7E=; h=Date:To:From:Subject:Message-Id; b=j7wpVpDvmvzKmEJcmezzMBudHV05QBSJdKSzHVnMTGAhUDuVjdhuIcx1hwHWk+ggVp5Ipxtp+5Tn9ntmOvOnRQGCs4gDSYrdsCdoDMZdDQjhmUd4+M9EG0F+mE3dfv8/c7kN1f24L1Z2pGDLQIH9hK4K2UKdAvyBjxM+Nvxr7OI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=OQkDeghp; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="OQkDeghp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAC001F0089D; Tue, 6 Oct 2026 23:44:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791330291; bh=/RMSxRO8H4GSIYiLp3iREUpLzqZA2YFmgRsyX2N2NYQ=; h=Date:To:From:Subject; b=OQkDeghp1OB4IP/jI+9rU2UyAJMQCdCzgU9kblt3qrtKM2Rd8XuUf06KiFQhevWDn xN01blKdeNncMUKmGZcvlGbSWczsG2j+HhkmmNAVIu6ERYw7tdF/dXxNiqDioRcTPL sjPxNodNvbw8hj9uAwM7SsMAu/CNHBYf0JnagK9M= Date: Tue, 06 Oct 2026 16:44:51 -0700 To: mm-commits@vger.kernel.org,vishal.moola@gmail.com,vbabka@kernel.org,surenb@google.com,stable@vger.kernel.org,rppt@kernel.org,rostedt@goodmis.org,mingo@kernel.org,mhocko@suse.com,ljs@kernel.org,liam@infradead.org,jgg@ziepe.ca,david@kernel.org,dave.hansen@linux.intel.com,baolu.lu@linux.intel.com,azpijr@gmail.com,akpm@linux-foundation.org,mikhail.v.gavrilov@gmail.com From: Andrew Morton Subject: [merged mm-hotfixes-stable] mm-dont-schedule-deferred-kernel-page-table-freeing-while-booting.patch removed from -mm tree Message-Id: <20261006234451.AAC001F0089D@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: don't schedule deferred kernel page table freeing while booting has been removed from the -mm tree. Its filename was mm-dont-schedule-deferred-kernel-page-table-freeing-while-booting.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Mikhail Gavrilov Subject: mm: don't schedule deferred kernel page table freeing while booting Date: Fri, 25 Sep 2026 10:06:47 +0500 Booting with a boot-time function tracer and a filter, for example ftrace=function ftrace_filter=pud_free_pmd_page panics on 7.3-rc4 as soon as the tracer starts: [ 23.531178] Starting tracer 'function' [ 23.675800] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] SMP KASAN NOPTI [ 23.819917] KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7] [ 23.964025] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.3.0-rc4-fe2ec83746e5-with-fixes-v2+ #195 PREEMPT(undef) [ 24.252248] RIP: 0010:__queue_work+0xab/0xf00 [ 25.981629] Call Trace: [ 26.125727] [ 26.413912] ? pagetable_free_kernel+0x20/0x120 [ 26.990283] queue_work_on+0x97/0xf0 [ 27.134382] __cpa_collapse_large_pages+0x501/0x6f0 [ 27.566662] cpa_flush+0x394/0x620 [ 27.998953] change_page_attr_set_clr+0x321/0x4a0 [ 29.151729] set_memory_rox+0xa2/0xf0 [ 29.584018] create_trampoline+0x431/0x6f0 ... [ 44.343347] Kernel panic - not syncing: Attempted to kill the idle task! The boot-time tracer is started from early_trace_init(), which runs before workqueue_init_early(). Making its trampoline read-only splits a large page, and CPA collapses it again right away. The split table has been a kernel page table since commit 9e4a3ec3411b ("x86/mm/pat: Allocate split page tables as kernel page tables"), so the collapse frees it through pagetable_free_kernel(), which queues work on system_percpu_wq - still NULL at that point. That commit is correct in itself; it only lets CPA reach pagetable_free_kernel() before the workqueue that function relies on exists. Keep putting the table on the list, but don't schedule the work while the system is still booting. A core_initcall schedules it once to free whatever was queued by then. Link: https://lore.kernel.org/20260925050647.86913-1-mikhail.v.gavrilov@gmail.com Link: https://lore.kernel.org/20260924064321.23787-1-mikhail.v.gavrilov@gmail.com Fixes: 9e4a3ec3411b ("x86/mm/pat: Allocate split page tables as kernel page tables") Signed-off-by: Mikhail Gavrilov Signed-off-by: Andrew Morton Suggested-by: David Hildenbrand (Arm) Suggested-by: Lorenzo Stoakes (ARM) Reviewed-by: Andrew Morton Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Jose A. Perez de Azpillaga Tested-by: Jose A. Perez de Azpillaga Cc: Dave Hansen Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Vishal Moola (Oracle) Cc: Ingo Molnar Cc: Lu Baolu Cc: Jason Gunthorpe Cc: Steven Rostedt Cc: --- mm/pgtable-generic.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) --- a/mm/pgtable-generic.c~mm-dont-schedule-deferred-kernel-page-table-freeing-while-booting +++ a/mm/pgtable-generic.c @@ -438,12 +438,30 @@ static void kernel_pgtable_work_func(str __pagetable_free(pt); } +static void schedule_kernel_pgtable_free(void) +{ + schedule_work(&kernel_pgtable_work.work); +} + void pagetable_free_kernel(struct ptdesc *pt) { spin_lock(&kernel_pgtable_work.lock); list_add(&pt->pt_list, &kernel_pgtable_work.list); spin_unlock(&kernel_pgtable_work.lock); - schedule_work(&kernel_pgtable_work.work); + /* + * The workqueue may not exist yet while the system is booting. + * kernel_pgtable_drain_early() schedules the work once it does. + */ + if (system_state != SYSTEM_BOOTING) + schedule_kernel_pgtable_free(); +} + +static int __init kernel_pgtable_drain_early(void) +{ + /* Free the kernel page tables queued while booting. */ + schedule_kernel_pgtable_free(); + return 0; } +core_initcall(kernel_pgtable_drain_early); #endif _ Patches currently in -mm which might be from mikhail.v.gavrilov@gmail.com are