From patchwork Mon Oct 16 15:19:05 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13423560 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 A0DE6CDB465 for ; Mon, 16 Oct 2023 15:19:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233832AbjJPPTq (ORCPT ); Mon, 16 Oct 2023 11:19:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233628AbjJPPTn (ORCPT ); Mon, 16 Oct 2023 11:19:43 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE70EE6 for ; Mon, 16 Oct 2023 08:19:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=MzyeUS8+Q6DyGG1BYkZOM8Vo8wKa2UEntgjHbKC7sqQ=; b=GJb2yG67l2i9wJHfLSPli4NmiV +WTJ+STZ9PvEtXrFika2dLjRUrokj2hMR900jok8EpQMettPN7gS3FHyPQKoznf647TUOpQSYHY87 7NhsXIonFGtW9kxXtw/WrFVNq3USbXjMFevv9C8aamNvWluW8r5OoAlCDIqIh2MY7r95iGlt3LwPy 5WsUY2qda44FfRXdd6nB2ta+X7WWj3YG/9DdMeQ3M++iT+3xJ8ubaNHJ4hpP0CAXaBOr6HpHe17qm Dw1r3eL81en6tel9bQMu5Y3fvInjNbKvWsdnZNPfP0uvJdUrEuS9xLq5kA/UMXrbV4xTXsKUFPxUa fbe12+bQ==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qsPNB-0067AI-2H; Mon, 16 Oct 2023 15:19:15 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qsPNC-0005na-07; Mon, 16 Oct 2023 16:19:14 +0100 From: David Woodhouse To: qemu-devel@nongnu.org Cc: Kevin Wolf , Hanna Reitz , Stefano Stabellini , Anthony Perard , Paul Durrant , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini , "Michael S. Tsirkin" , Marcel Apfelbaum , Richard Henderson , Eduardo Habkost , David Woodhouse , Marcelo Tosatti , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org Subject: [PATCH 08/12] hw/xen: do not repeatedly try to create a failing backend device Date: Mon, 16 Oct 2023 16:19:05 +0100 Message-Id: <20231016151909.22133-9-dwmw2@infradead.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231016151909.22133-1-dwmw2@infradead.org> References: <20231016151909.22133-1-dwmw2@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse If xen_backend_device_create() fails to instantiate a device, the XenBus code will just keep trying over and over again each time the bus is re-enumerated, as long as the backend appears online and in XenbusStateInitialising. The only thing which prevents the XenBus code from recreating duplicates of devices which already exist, is the fact that xen_device_realize() sets the backend state to XenbusStateInitWait. If the attempt to create the device doesn't get *that* far, that's when it will keep getting retried. My first thought was to handle errors by setting the backend state to XenbusStateClosed, but that doesn't work for XenConsole which wants to *ignore* any device of type != "ioemu" completely. So, make xen_backend_device_create() *keep* the XenBackendInstance for a failed device, and provide a new xen_backend_exists() function to allow xen_bus_type_enumerate() to check whether one already exists before creating a new one. Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant --- hw/xen/xen-backend.c | 27 +++++++++++++++++++++------ hw/xen/xen-bus.c | 3 ++- include/hw/xen/xen-backend.h | 1 + 3 files changed, 24 insertions(+), 7 deletions(-) diff --git a/hw/xen/xen-backend.c b/hw/xen/xen-backend.c index 5b0fb76eae..b9bf70a9f5 100644 --- a/hw/xen/xen-backend.c +++ b/hw/xen/xen-backend.c @@ -101,6 +101,24 @@ static XenBackendInstance *xen_backend_list_find(XenDevice *xendev) return NULL; } +bool xen_backend_exists(const char *type, const char *name) +{ + const XenBackendImpl *impl = xen_backend_table_lookup(type); + XenBackendInstance *backend; + + if (!impl) { + return false; + } + + QLIST_FOREACH(backend, &backend_list, entry) { + if (backend->impl == impl && !strcmp(backend->name, name)) { + return true; + } + } + + return false; +} + static void xen_backend_list_remove(XenBackendInstance *backend) { QLIST_REMOVE(backend, entry); @@ -122,11 +140,6 @@ void xen_backend_device_create(XenBus *xenbus, const char *type, backend->name = g_strdup(name); impl->create(backend, opts, errp); - if (*errp) { - g_free(backend->name); - g_free(backend); - return; - } backend->impl = impl; xen_backend_list_add(backend); @@ -165,7 +178,9 @@ bool xen_backend_try_device_destroy(XenDevice *xendev, Error **errp) } impl = backend->impl; - impl->destroy(backend, errp); + if (backend->xendev) { + impl->destroy(backend, errp); + } xen_backend_list_remove(backend); g_free(backend->name); diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index cc524ed92c..0da2aa219a 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -209,7 +209,8 @@ static void xen_bus_type_enumerate(XenBus *xenbus, const char *type) NULL, "%u", &online) != 1) online = 0; - if (online && state == XenbusStateInitialising) { + if (online && state == XenbusStateInitialising && + !xen_backend_exists(type, backend[i])) { Error *local_err = NULL; xen_bus_backend_create(xenbus, type, backend[i], backend_path, diff --git a/include/hw/xen/xen-backend.h b/include/hw/xen/xen-backend.h index aac2fd454d..0f01631ae7 100644 --- a/include/hw/xen/xen-backend.h +++ b/include/hw/xen/xen-backend.h @@ -33,6 +33,7 @@ XenDevice *xen_backend_get_device(XenBackendInstance *backend); void xen_backend_register(const XenBackendInfo *info); const char **xen_backend_get_types(unsigned int *nr); +bool xen_backend_exists(const char *type, const char *name); void xen_backend_device_create(XenBus *xenbus, const char *type, const char *name, QDict *opts, Error **errp); bool xen_backend_try_device_destroy(XenDevice *xendev, Error **errp);