From patchwork Thu Nov 9 13:42:38 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 1862042 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=patchwork.ozlabs.org) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4SR3PS35yBz1yQl for ; Fri, 10 Nov 2023 00:55:24 +1100 (AEDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r15Nk-0000Hw-0a; Thu, 09 Nov 2023 08:47:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r15Me-00079k-RJ; Thu, 09 Nov 2023 08:46:36 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r15Mc-0001zt-31; Thu, 09 Nov 2023 08:46:31 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 2A15031B1A; Thu, 9 Nov 2023 16:43:14 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id 3AB15344C0; Thu, 9 Nov 2023 16:43:06 +0300 (MSK) Received: (nullmailer pid 1461864 invoked by uid 1000); Thu, 09 Nov 2023 13:43:02 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, David Woodhouse , Paul Durrant , Michael Tokarev Subject: [Stable-8.1.3 34/55] hw/xen: fix XenStore watch delivery to guest Date: Thu, 9 Nov 2023 16:42:38 +0300 Message-Id: <20231109134300.1461632-34-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: David Woodhouse When fire_watch_cb() found the response buffer empty, it would call deliver_watch() to generate the XS_WATCH_EVENT message in the response buffer and send an event channel notification to the guest… without actually *copying* the response buffer into the ring. So there was nothing for the guest to see. The pending response didn't actually get processed into the ring until the guest next triggered some activity from its side. Add the missing call to put_rsp(). It might have been slightly nicer to call xen_xenstore_event() here, which would *almost* have worked. Except for the fact that it calls xen_be_evtchn_pending() to check that it really does have an event pending (and clear the eventfd for next time). And under Xen it's defined that setting that fd to O_NONBLOCK isn't guaranteed to work, so the emu implementation follows suit. This fixes Xen device hot-unplug. Cc: qemu-stable@nongnu.org Fixes: 0254c4d19df ("hw/xen: Add xenstore wire implementation and implementation stubs") Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant (cherry picked from commit 4a5780f52095f1daf23618dc6198a2a1665ea505) Signed-off-by: Michael Tokarev diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c index 133d89e953..725ca2f15d 100644 --- a/hw/i386/kvm/xen_xenstore.c +++ b/hw/i386/kvm/xen_xenstore.c @@ -1357,10 +1357,12 @@ static void fire_watch_cb(void *opaque, const char *path, const char *token) } else { deliver_watch(s, path, token); /* - * If the message was queued because there was already ring activity, - * no need to wake the guest. But if not, we need to send the evtchn. + * Attempt to queue the message into the actual ring, and send + * the event channel notification if any bytes are copied. */ - xen_be_evtchn_notify(s->eh, s->be_port); + if (s->rsp_pending && put_rsp(s) > 0) { + xen_be_evtchn_notify(s->eh, s->be_port); + } } }