From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756516Ab2HOUcr (ORCPT ); Wed, 15 Aug 2012 16:32:47 -0400 Received: from mail.windriver.com ([147.11.1.11]:36515 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756368Ab2HOTtg (ORCPT ); Wed, 15 Aug 2012 15:49:36 -0400 From: Paul Gortmaker To: , CC: Igor Mammedov , Konrad Rzeszutek Wilk , Paul Gortmaker Subject: [v2.6.34-stable 032/165] xen: x86_32: do not enable iterrupts when returning from exception in interrupt context Date: Wed, 15 Aug 2012 15:46:16 -0400 Message-ID: <1345060109-9187-33-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.12.rc2 In-Reply-To: <1345060109-9187-1-git-send-email-paul.gortmaker@windriver.com> References: <1345060109-9187-1-git-send-email-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Igor Mammedov ------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. ------------------- commit d198d499148a0c64a41b3aba9e7dd43772832b91 upstream. If vmalloc page_fault happens inside of interrupt handler with interrupts disabled then on exit path from exception handler when there is no pending interrupts, the following code (arch/x86/xen/xen-asm_32.S:112): cmpw $0x0001, XEN_vcpu_info_pending(%eax) sete XEN_vcpu_info_mask(%eax) will enable interrupts even if they has been previously disabled according to eflags from the bounce frame (arch/x86/xen/xen-asm_32.S:99) testb $X86_EFLAGS_IF>>8, 8+1+ESP_OFFSET(%esp) setz XEN_vcpu_info_mask(%eax) Solution is in setting XEN_vcpu_info_mask only when it should be set according to cmpw $0x0001, XEN_vcpu_info_pending(%eax) but not clearing it if there isn't any pending events. Reproducer for bug is attached to RHBZ 707552 Signed-off-by: Igor Mammedov Acked-by: Jeremy Fitzhardinge Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Paul Gortmaker --- arch/x86/xen/xen-asm_32.S | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S index 22a2093..b040b0e 100644 --- a/arch/x86/xen/xen-asm_32.S +++ b/arch/x86/xen/xen-asm_32.S @@ -113,11 +113,13 @@ xen_iret_start_crit: /* * If there's something pending, mask events again so we can - * jump back into xen_hypervisor_callback + * jump back into xen_hypervisor_callback. Otherwise do not + * touch XEN_vcpu_info_mask. */ - sete XEN_vcpu_info_mask(%eax) + jne 1f + movb $1, XEN_vcpu_info_mask(%eax) - popl %eax +1: popl %eax /* * From this point on the registers are restored and the stack -- 1.7.12.rc2