From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 38136400978 for ; Mon, 3 Aug 2026 12:41:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785760913; cv=none; b=uCYVIJRiJt+JFBRu/oVczzTciOieN0mqdfIo700nO8veyRlKcRXJULzKaUMjrtNlcWSwBpVC1JRGMokc8MkwnmJVG6+5LKfklDgliuWwGFPyyEVT3UHRk3J1MZ+11kxrT2jPpnJwbQg+2kReynZSqcOiq8UBUvPd019oqhZ/0YI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785760913; c=relaxed/simple; bh=VtwXvO03/d0Np5b75y/sGJIOp+lh4BJuGwz96xd5TZQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YlsNq3xMvJFHLUT71RmBCxm+YY/wf9se81mP5txQBrQWWjHa6SbaMcbq3CtMCUmvJGBOOGRwTQHVZ6GQo84gDca/NZufG60TG/Q5aSlNt0/KJRdX/+WiLFTFOifQDi0bOHQgOdikRnlONpwH3DizJnOdkaUGqdRmI7xk8g9cL0I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=YndVUhhs; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=rxaAgSfH; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=T+pUauja; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=DUEa6KbP; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="YndVUhhs"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="rxaAgSfH"; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="T+pUauja"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="DUEa6KbP" Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 18F377F0E6; Mon, 3 Aug 2026 12:41:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1785760905; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1ODL6gCk8lof5B/HMStAKTE/E0Vq5yUl2rgXGKUHBio=; b=YndVUhhsn6D+xFCay2LMawar+ReWclRkw0K5TrxNoDo7HKj5P8kfn0p0wA/kIrgVjguYEn B+7gcaYxJpC0ouMiWbRla7tPefR4OAs8tfvZZUeDV9Of2cI0eqoV7AM/2coLKtyeQ7xSmD 7T045LAIgwFm39g+PRGd0J6xQ+Pg6ec= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1785760905; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1ODL6gCk8lof5B/HMStAKTE/E0Vq5yUl2rgXGKUHBio=; b=rxaAgSfHajmj2MULUhqVM9DoGPlRJIjG+f6wT/HWG2LWYwll1qfjEjP0FCZ7J/Ivf/QNa0 F0Mq+25xMD/Oc3Dg== Authentication-Results: smtp-out1.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1785760901; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1ODL6gCk8lof5B/HMStAKTE/E0Vq5yUl2rgXGKUHBio=; b=T+pUaujadhUEuzF7AIYqqNeI6LapYg3PXnwUPFVlo/5vy3LGvd9eDpA2VA+oj5/0MAM3Wt nkAR7pCNV/J21jLpSIWw8/ri5F+floyzpUlreyhWtzY57kOO0hynLtsAmj/M5aU+VxsOU2 4XbNneXfDF6WIeoM6SU79ltF5/7nWMQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1785760901; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1ODL6gCk8lof5B/HMStAKTE/E0Vq5yUl2rgXGKUHBio=; b=DUEa6KbPFzZTiB+sI1npko+DVVChlHKpZ9fVEgKgILoCLtiKoqwKNh0nsyLI2RubGfRQEn 6m+G7cmj6hao5DCQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 14A75779A1; Mon, 3 Aug 2026 12:41:39 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 98s4AYOMcGpuWAAAD6G6ig (envelope-from ); Mon, 03 Aug 2026 12:41:39 +0000 Date: Mon, 3 Aug 2026 13:41:37 +0100 From: Pedro Falcato To: Steffen Dirkwinkel , "Mike Rapoport (Microsoft)" Cc: Dave Hansen , "Denis V. Lunev" , Andrew Morton , Andy Lutomirski , Borislav Petkov , David CARLIER , David Hildenbrand , Ingo Molnar , Jason Gunthorpe , Juergen Gross , Kevin Tian , Kiryl Shutsemau , "Liam R. Howlett" , Lorenzo Stoakes , Lu Baolu , "H. Peter Anvin" , Peter Zijlstra , Shakeel Butt , Suren Baghdasaryan , Thomas Gleixner , Toshi Kani , Vishal Moola , Vlastimil Babka , Will Deacon , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org, syzbot@syzkaller.appspotmail.com, Jiri Slaby Subject: Re: [PATCH 0/5] x86/mm/pat: CPA fixes Message-ID: References: <20260728-cpa-fixes-v1-0-2ed2352300b3@kernel.org> <555ea1d43a12c30a8f1eaf10c899b3790d728f33.camel@dirkwinkel.cc> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="bh5jbue2ogdsvams" Content-Disposition: inline In-Reply-To: <555ea1d43a12c30a8f1eaf10c899b3790d728f33.camel@dirkwinkel.cc> X-Spam-Score: -2.30 X-Spam-Level: X-Spam-Flag: NO X-Spamd-Result: default: False [-2.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[multipart/mixed,text/plain,text/x-patch]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+,1:+,2:+]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; RCPT_COUNT_TWELVE(0.00)[33]; RCVD_TLS_ALL(0.00)[]; URIBL_BLOCKED(0.00)[steffen.cc:email,opensuse.org:url,suse.de:email,imap1.dmz-prg2.suse.org:helo]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[linux.intel.com,openvz.org,linux-foundation.org,kernel.org,alien8.de,gmail.com,redhat.com,ziepe.ca,suse.com,intel.com,infradead.org,zytor.com,linux.dev,google.com,hpe.com,lists.linux.dev,vger.kernel.org,kvack.org,syzkaller.appspotmail.com]; R_RATELIMIT(0.00)[to_ip_from(RL3mhzhn45zpqpmgqn4z7synfm)]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,steffen.cc:email,opensuse.org:url,imap1.dmz-prg2.suse.org:helo]; RCVD_COUNT_TWO(0.00)[2]; HAS_ATTACHMENT(0.00)[] --bh5jbue2ogdsvams Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Jul 30, 2026 at 05:53:50PM +0200, Steffen Dirkwinkel wrote: > Hello, > > > On Tue, 2026-07-28 at 16:07 +0300, Mike Rapoport (Microsoft) wrote: > > There are a couple of CPA fixes floating around: > > > > Denis Lunev fixed races between split and collapse of the large mappings: > > > > https://lore.kernel.org/all/20260715183453.2381141-1-den@openvz.org > > We saw the error below and I was wondering if it might be related to these fixes > or a similar case that's unfixed still. Seems to have happened during concurrent > kernel module loading of kvm and i915 (similar to the case in the patch from > Denis Lunev). But we got it without KASAN and the stack looks a little > different. I was not able to reproduce this with a ~16 hour concurrent module > load unload loop so far. > > Kernel: v7.1.5, PREEMPT_RT, tainted because of /dev/msr access > CPU: Elkhart Lake Atom X6214RE, 2 cores, isolcpus=1-N > > ------------[ cut here ]------------ > kernel BUG at arch/x86/kernel/alternative.c:2644! > Oops: invalid opcode: 0000 [#1] SMP NOPTI > CPU: 0 UID: 0 PID: 559 Comm: (udev-worker) Tainted: G S 7.1.5- > rt1-bhf-369933-f1a4ee1dd787 #1 PREEMPT_{RT,(lazy)} > Tainted: [S]=CPU_OUT_OF_SPEC > RIP: 0010:__text_poke+0x356/0x3d0 > Call Trace: > > smp_text_poke_batch_finish+0x1aa/0x3a0 > ? vmx_switch_vmcs+0xc8/0xd0 [kvm_intel] > __static_call_transform+0xfa/0x1f0 > ? vmx_switch_vmcs+0xc8/0xd0 [kvm_intel] > ? __pfx_preempt_schedule_thunk+0x10/0x10 > arch_static_call_transform+0x57/0xa0 > ? vmx_switch_vmcs+0xc8/0xd0 [kvm_intel] > __static_call_init+0x1aa/0x230 > ? __SCT__tp_func_kvm_mmu_split_huge_page+0x8/0x8 > ? __SCT__tp_func_kvm_mmu_split_huge_page+0x8/0x8 > static_call_module_notify+0x11f/0x150 We're also observing something very similar downstream (https://bugzilla.opensuse.org/show_bug.cgi?id=1271202) on 7.1.3 kernels, on our QA infra. I wrote a patch that should fix it (I didn't get to test it yet, since this didn't hit mainline/stable yet), on top of this. Mike, do you mind throwing it on top of this series, or should I submit separately? -- Pedro --bh5jbue2ogdsvams Content-Type: text/x-patch; charset=us-ascii Content-Disposition: attachment; filename="0001-x86-alternative-exclude-text-poking-against-change_p.patch" >From 0a483fd05fda6e3953861b722995b58daf4878ef Mon Sep 17 00:00:00 2001 From: Pedro Falcato Date: Mon, 3 Aug 2026 13:16:25 +0100 Subject: [PATCH] x86/alternative: exclude text poking against change_page_attr() >From time to time, the following BUG can be observed[0]: > kernel BUG at arch/x86/kernel/alternative.c:2576! > Oops: invalid opcode: 0000 [#1] SMP NOPTI > CPU: 0 UID: 0 PID: 355 Comm: (udev-worker) Not tainted 7.1.3-1-default #1 PREEMPT(full) openSUSE Tumbleweed 8c1795b03ec64f997e57a8ad38b1161e3b98da64 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022 > RIP: 0010:__text_poke+0x2aa/0x450 > Call Trace: > > smp_text_poke_batch_finish+0x2a7/0x320 > __static_call_transform+0xb7/0x220 > arch_static_call_transform+0x5b/0xb0 > __static_call_init+0xe9/0x270 > static_call_module_notify+0x11f/0x150 > notifier_call_chain+0x61/0xe0 > blocking_notifier_call_chain_robust+0x63/0xc0 > load_module+0x1c92/0x20c0 > init_module_from_file+0xd8/0x140 > idempotent_init_module+0x100/0x2f0 > __x64_sys_finit_module+0x71/0xe0 > do_syscall_64+0xe1/0x610 > entry_SYSCALL_64_after_hwframe+0x76/0x7e which matches the following BUG_ON in alternative.c: /* * If something went wrong, crash and burn since recovery paths are not * implemented. */ BUG_ON(!pages[0] || (cross_page_boundary && !pages[1])); This can happen if vmalloc_to_page() fails, for any reason. Such can happen if text poking races with CPA, which can possibly result in the collapsing of page tables (or breaking of PMD hugepages). It is not a problem for most users of vmalloc_to_page() (they solely own the vmalloc'd range) but, when CONFIG_ARCH_HAS_EXECMEM_ROX=y, various modules own a single execmem vmalloc range, and can call set_memory_*() in parallel on it. This can happen to race against __text_poke and cause havoc in vmalloc_to_page(). Fix it by excluding against CPA using the init_mm mmap read lock. Fixes: 64f6a4e10c05 ("x86: re-enable EXECMEM_ROX support") Reported-by: Jiri Slaby Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1271202 [0] Reported-by: Steffen Dirkwinkel Link: https://lore.kernel.org/linux-mm/555ea1d43a12c30a8f1eaf10c899b3790d728f33.camel@dirkwinkel.cc/ Cc: stable@vger.kernel.org Signed-off-by: Pedro Falcato --- arch/x86/kernel/alternative.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 62936a3bde19..9071eb870eab 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -2559,6 +2559,14 @@ static void *__text_poke(text_poke_f func, void *addr, const void *src, size_t l */ BUG_ON(!after_bootmem); + /* + * Exclude against change_page_attr() collapse in execmem ROX regions. + * These are PMD sized and this module may not own the whole PMD, + * thus breakdown/collapse may happen at any moment by concurrent module + * loading, which races with vmalloc_to_page(). + */ + guard(mmap_read_lock)(&init_mm); + if (!core_kernel_text((unsigned long)addr)) { pages[0] = vmalloc_to_page(addr); if (cross_page_boundary) -- 2.55.0 --bh5jbue2ogdsvams--