From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1292CC43441 for ; Mon, 19 Nov 2018 16:57:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CED5F2148E for ; Mon, 19 Nov 2018 16:57:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="asJMeX2P" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CED5F2148E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404675AbeKTDWL (ORCPT ); Mon, 19 Nov 2018 22:22:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:33752 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403956AbeKTDWK (ORCPT ); Mon, 19 Nov 2018 22:22:10 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 74458208E3; Mon, 19 Nov 2018 16:57:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542646675; bh=itjEC9+QHmmh2n5VFDaXGfihq9GeRTwtH8YfBl8I8BA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=asJMeX2PGRcKWiv8gKRJTWwTnhKUBvUe+Cv3BgPwgBg3SelxzbTA025Cy8vApB4WC h2KxN/rDtr6AGp6+F/T4J+QTW6SgyCACOyYcQNLRfy1GLa7ZYkcDl3EOL3xg8R6E9M lrN87p8yVldlfh3Jt3SBdHTqXhoi4TfukK1AY0Zc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Waiman.Long@hp.com, peterz@infradead.org, Juergen Gross , Jan Beulich Subject: [PATCH 4.4 047/160] xen: make xen_qlock_wait() nestable Date: Mon, 19 Nov 2018 17:28:06 +0100 Message-Id: <20181119162636.052931540@linuxfoundation.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181119162630.031306128@linuxfoundation.org> References: <20181119162630.031306128@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Juergen Gross commit a856531951dc8094359dfdac21d59cee5969c18e upstream. xen_qlock_wait() isn't safe for nested calls due to interrupts. A call of xen_qlock_kick() might be ignored in case a deeper nesting level was active right before the call of xen_poll_irq(): CPU 1: CPU 2: spin_lock(lock1) spin_lock(lock1) -> xen_qlock_wait() -> xen_clear_irq_pending() Interrupt happens spin_unlock(lock1) -> xen_qlock_kick(CPU 2) spin_lock_irqsave(lock2) spin_lock_irqsave(lock2) -> xen_qlock_wait() -> xen_clear_irq_pending() clears kick for lock1 -> xen_poll_irq() spin_unlock_irq_restore(lock2) -> xen_qlock_kick(CPU 2) wakes up spin_unlock_irq_restore(lock2) IRET resumes in xen_qlock_wait() -> xen_poll_irq() never wakes up The solution is to disable interrupts in xen_qlock_wait() and not to poll for the irq in case xen_qlock_wait() is called in nmi context. Cc: stable@vger.kernel.org Cc: Waiman.Long@hp.com Cc: peterz@infradead.org Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman --- arch/x86/xen/spinlock.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -41,29 +41,25 @@ static void xen_qlock_kick(int cpu) */ static void xen_qlock_wait(u8 *byte, u8 val) { + unsigned long flags; int irq = __this_cpu_read(lock_kicker_irq); /* If kicker interrupts not initialized yet, just spin */ - if (irq == -1) + if (irq == -1 || in_nmi()) return; - /* If irq pending already clear it and return. */ + /* Guard against reentry. */ + local_irq_save(flags); + + /* If irq pending already clear it. */ if (xen_test_irq_pending(irq)) { xen_clear_irq_pending(irq); - return; + } else if (READ_ONCE(*byte) == val) { + /* Block until irq becomes pending (or a spurious wakeup) */ + xen_poll_irq(irq); } - if (READ_ONCE(*byte) != val) - return; - - /* - * If an interrupt happens here, it will leave the wakeup irq - * pending, which will cause xen_poll_irq() to return - * immediately. - */ - - /* Block until irq becomes pending (or perhaps a spurious wakeup) */ - xen_poll_irq(irq); + local_irq_restore(flags); } #else /* CONFIG_QUEUED_SPINLOCKS */