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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 888F2C25B07 for ; Tue, 9 Aug 2022 18:19:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345544AbiHISTB (ORCPT ); Tue, 9 Aug 2022 14:19:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346741AbiHISRf (ORCPT ); Tue, 9 Aug 2022 14:17:35 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D57282ED4F; Tue, 9 Aug 2022 11:06:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A62FCB8188F; Tue, 9 Aug 2022 18:06:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAC6BC433C1; Tue, 9 Aug 2022 18:06:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660068384; bh=mqbC7bVhIM0dnxYNVzszPMiYzv0AKKldGP1tDyqt/kk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G04DlaKk5aKiV38CAoLzgjFBvDH4mTSob9yKXD1cc9HydSy5J9AOjakGjSj/keXSI lWnrdQC9cGGsgQO5wuQPjg1yEErfHRkw7owo0RfNRjFJroqrrESHLlNGqK6Y+iwIvb NtyeE89nIK9NM7dM3IY6wr6sB44ramnX2nGKrZrY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Eric W. Biederman" , Petr Mladek , Seth Forshee , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.18 12/35] entry/kvm: Exit to user mode when TIF_NOTIFY_SIGNAL is set Date: Tue, 9 Aug 2022 20:00:41 +0200 Message-Id: <20220809175515.512110504@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220809175515.046484486@linuxfoundation.org> References: <20220809175515.046484486@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Seth Forshee [ Upstream commit 3e684903a8574ffc9475fdf13c4780a7adb506ad ] A livepatch transition may stall indefinitely when a kvm vCPU is heavily loaded. To the host, the vCPU task is a user thread which is spending a very long time in the ioctl(KVM_RUN) syscall. During livepatch transition, set_notify_signal() will be called on such tasks to interrupt the syscall so that the task can be transitioned. This interrupts guest execution, but when xfer_to_guest_mode_work() sees that TIF_NOTIFY_SIGNAL is set but not TIF_SIGPENDING it concludes that an exit to user mode is unnecessary, and guest execution is resumed without transitioning the task for the livepatch. This handling of TIF_NOTIFY_SIGNAL is incorrect, as set_notify_signal() is expected to break tasks out of interruptible kernel loops and cause them to return to userspace. Change xfer_to_guest_mode_work() to handle TIF_NOTIFY_SIGNAL the same as TIF_SIGPENDING, signaling to the vCPU run loop that an exit to userpsace is needed. Any pending task_work will be run when get_signal() is called from exit_to_user_mode_loop(), so there is no longer any need to run task work from xfer_to_guest_mode_work(). Suggested-by: "Eric W. Biederman" Cc: Petr Mladek Signed-off-by: Seth Forshee Message-Id: <20220504180840.2907296-1-sforshee@digitalocean.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- kernel/entry/kvm.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c index 9d09f489b60e..2e0f75bcb7fd 100644 --- a/kernel/entry/kvm.c +++ b/kernel/entry/kvm.c @@ -9,12 +9,6 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) int ret; if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) { - clear_notify_signal(); - if (task_work_pending(current)) - task_work_run(); - } - - if (ti_work & _TIF_SIGPENDING) { kvm_handle_signal_exit(vcpu); return -EINTR; } -- 2.35.1