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=-6.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no 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 E4731C433DF for ; Mon, 24 Aug 2020 08:23:21 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B25E020738 for ; Mon, 24 Aug 2020 08:23:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="sf45wCYw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B25E020738 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kA7l1-0006kk-BT; Mon, 24 Aug 2020 08:23:11 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kA7l0-0006kW-JE for xen-devel@lists.xenproject.org; Mon, 24 Aug 2020 08:23:10 +0000 X-Inumbo-ID: e51dde3f-b1d7-489c-b47b-e796deb8438f Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id e51dde3f-b1d7-489c-b47b-e796deb8438f; Mon, 24 Aug 2020 08:23:09 +0000 (UTC) Received: from localhost (83-86-89-107.cable.dynamic.v4.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 6D3222074D; Mon, 24 Aug 2020 08:23:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598257389; bh=3wq/MzR5NmEmGgG2m19J3rMTZjVfVRsvtF2yyDmKKKk=; h=Subject:To:Cc:From:Date:In-Reply-To:From; b=sf45wCYws+hinuQoVIErYLO6D1IXedfCqDTtqRY+tuOVIFb6d32vPud381jGk82as ldN7xBcmAfAhJMYlkRWjhz40VvH1UFv7JP4iHHu+nowt/alHfMT7Bv0ZQvr06e3xQM RxMruQLhft6Y81HKhLlc+QD04UqgCH1dv7KkTnIA= Subject: Patch "xen: don't reschedule in preemption off sections" has been added to the 5.7-stable tree To: boris.ostrovsky@oracle.com, cmb@prgmr.com, gregkh@linuxfoundation.org, jgross@suse.com, srn@prgmr.com, sstabellini@kernel.org, xen-devel@lists.xenproject.org Cc: From: Date: Mon, 24 Aug 2020 10:23:27 +0200 In-Reply-To: <20200820065908.20592-1-jgross@suse.com> Message-ID: <15982574071316@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit X-stable: commit X-Patchwork-Hint: ignore X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" This is a note to let you know that I've just added the patch titled xen: don't reschedule in preemption off sections to the 5.7-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: xen-don-t-reschedule-in-preemption-off-sections.patch and it can be found in the queue-5.7 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >From jgross@suse.com Mon Aug 24 10:12:00 2020 From: Juergen Gross Date: Thu, 20 Aug 2020 08:59:08 +0200 Subject: xen: don't reschedule in preemption off sections To: stable@vger.kernel.org Cc: xen-devel@lists.xenproject.org, Juergen Gross , Boris Ostrovsky , Stefano Stabellini , Sarah Newman , Chris Brannon Message-ID: <20200820065908.20592-1-jgross@suse.com> From: Juergen Gross For support of long running hypercalls xen_maybe_preempt_hcall() is calling cond_resched() in case a hypercall marked as preemptible has been interrupted. Normally this is no problem, as only hypercalls done via some ioctl()s are marked to be preemptible. In rare cases when during such a preemptible hypercall an interrupt occurs and any softirq action is started from irq_exit(), a further hypercall issued by the softirq handler will be regarded to be preemptible, too. This might lead to rescheduling in spite of the softirq handler potentially having set preempt_disable(), leading to splats like: BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl INFO: lockdep is turned off. CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1 Call Trace: dump_stack+0x8f/0xd0 ___might_sleep.cold.76+0xb2/0x103 xen_maybe_preempt_hcall+0x48/0x70 xen_do_hypervisor_callback+0x37/0x40 RIP: e030:xen_hypercall_xen_version+0xa/0x20 Code: ... RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246 RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0 R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000 ? xen_hypercall_xen_version+0xa/0x20 ? xen_force_evtchn_callback+0x9/0x10 ? check_events+0x12/0x20 ? xen_restore_fl_direct+0x1f/0x20 ? _raw_spin_unlock_irqrestore+0x53/0x60 ? debug_dma_sync_single_for_cpu+0x91/0xc0 ? _raw_spin_unlock_irqrestore+0x53/0x60 ? xen_swiotlb_sync_single_for_cpu+0x3d/0x140 ? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en] ? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en] ? net_rx_action+0x151/0x4a0 ? __do_softirq+0xed/0x55b ? irq_exit+0xea/0x100 ? xen_evtchn_do_upcall+0x2c/0x40 ? xen_do_hypervisor_callback+0x29/0x40 ? xen_hypercall_domctl+0xa/0x20 ? xen_hypercall_domctl+0x8/0x20 ? privcmd_ioctl+0x221/0x990 [xen_privcmd] ? do_vfs_ioctl+0xa5/0x6f0 ? ksys_ioctl+0x60/0x90 ? trace_hardirqs_off_thunk+0x1a/0x20 ? __x64_sys_ioctl+0x16/0x20 ? do_syscall_64+0x62/0x250 ? entry_SYSCALL_64_after_hwframe+0x49/0xbe Fix that by testing preempt_count() before calling cond_resched(). In kernel 5.8 this can't happen any more due to the entry code rework (more than 100 patches, so not a candidate for backporting). The issue was introduced in kernel 4.3, so this patch should go into all stable kernels in [4.3 ... 5.7]. Reported-by: Sarah Newman Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()") Cc: Sarah Newman Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross Tested-by: Chris Brannon Signed-off-by: Greg Kroah-Hartman --- drivers/xen/preempt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/xen/preempt.c +++ b/drivers/xen/preempt.c @@ -27,7 +27,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca asmlinkage __visible void xen_maybe_preempt_hcall(void) { if (unlikely(__this_cpu_read(xen_in_preemptible_hcall) - && need_resched())) { + && need_resched() && !preempt_count())) { /* * Clear flag as we may be rescheduled on a different * cpu. Patches currently in stable-queue which might be from jgross@suse.com are queue-5.7/fix-build-error-when-config_acpi-is-not-set-enabled.patch queue-5.7/xen-don-t-reschedule-in-preemption-off-sections.patch queue-5.7/efi-avoid-error-message-when-booting-under-xen.patch queue-5.7/swiotlb-xen-use-vmalloc_to_page-on-vmalloc-virt-addr.patch