Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751347Ab3CWNh3 (ORCPT ); Sat, 23 Mar 2013 09:37:29 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:44846 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751021Ab3CWNhZ (ORCPT ); Sat, 23 Mar 2013 09:37:25 -0400 From: Konrad Rzeszutek Wilk To: xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, hpa@zytor.com Cc: mingo@redhat.com, tglx@linutronix.de, rostedt@goodmis.org, kraman@redhat.com, gregkh@linuxfoundation.org, bp@alien8.de, samu.kallio@aberdeencloud.com, stable@vger.kernel.org, Konrad Rzeszutek Wilk Subject: [PATCH 1/2] x86: mm: Fix vmalloc_fault oops during lazy MMU updates. Date: Sat, 23 Mar 2013 09:36:35 -0400 Message-Id: <1364045796-10720-1-git-send-email-konrad.wilk@oracle.com> X-Mailer: git-send-email 1.8.0.2 In-Reply-To: <9a798a0e-bc39-40db-be7f-b5e6fcc382d9@email.android.com> References: <9a798a0e-bc39-40db-be7f-b5e6fcc382d9@email.android.com> X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3293 Lines: 88 From: Samu Kallio In paravirtualized x86_64 kernels, vmalloc_fault may cause an oops when lazy MMU updates are enabled, because set_pgd effects are being deferred. One instance of this problem is during process mm cleanup with memory cgroups enabled. The chain of events is as follows: - zap_pte_range enables lazy MMU updates - zap_pte_range eventually calls mem_cgroup_charge_statistics, which accesses the vmalloc'd mem_cgroup per-cpu stat area - vmalloc_fault is triggered which tries to sync the corresponding PGD entry with set_pgd, but the update is deferred - vmalloc_fault oopses due to a mismatch in the PUD entries The OOPs usually looks as so: ------------[ cut here ]------------ kernel BUG at arch/x86/mm/fault.c:396! invalid opcode: 0000 [#1] SMP .. snip .. CPU 1 Pid: 10866, comm: httpd Not tainted 3.6.10-4.fc18.x86_64 #1 RIP: e030:[] [] vmalloc_fault+0x11f/0x208 .. snip .. Call Trace: [] do_page_fault+0x399/0x4b0 [] ? xen_mc_extend_args+0xec/0x110 [] page_fault+0x25/0x30 [] ? mem_cgroup_charge_statistics.isra.13+0x13/0x50 [] __mem_cgroup_uncharge_common+0xd8/0x350 [] mem_cgroup_uncharge_page+0x57/0x60 [] page_remove_rmap+0xe0/0x150 [] ? vm_normal_page+0x1a/0x80 [] unmap_single_vma+0x531/0x870 [] unmap_vmas+0x52/0xa0 [] ? pte_mfn_to_pfn+0x72/0x100 [] exit_mmap+0x98/0x170 [] ? __raw_callee_save_xen_pmd_val+0x11/0x1e [] mmput+0x83/0xf0 [] exit_mm+0x104/0x130 [] do_exit+0x15a/0x8c0 [] do_group_exit+0x3f/0xa0 [] sys_exit_group+0x17/0x20 [] system_call_fastpath+0x16/0x1b Calling arch_flush_lazy_mmu_mode immediately after set_pgd makes the changes visible to the consistency checks. CC: stable@vger.kernel.org RedHat-Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=914737 Tested-by: Josh Boyer Reported-and-Tested-by: Krishna Raman Signed-off-by: Samu Kallio Tested-by: Konrad Rzeszutek Wilk Signed-off-by: Konrad Rzeszutek Wilk --- arch/x86/mm/fault.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 2b97525..0e88336 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -378,10 +378,12 @@ static noinline __kprobes int vmalloc_fault(unsigned long address) if (pgd_none(*pgd_ref)) return -1; - if (pgd_none(*pgd)) + if (pgd_none(*pgd)) { set_pgd(pgd, *pgd_ref); - else + arch_flush_lazy_mmu_mode(); + } else { BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); + } /* * Below here mismatches are bugs because these lower tables -- 1.8.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/