From patchwork Mon Nov 6 14:34:58 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13447011 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8E8CA28DAF for ; Mon, 6 Nov 2023 14:36:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from smtp-fw-52002.amazon.com (smtp-fw-52002.amazon.com [52.119.213.150]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2AA2094 for ; Mon, 6 Nov 2023 06:36:02 -0800 (PST) X-IronPort-AV: E=Sophos;i="6.03,281,1694736000"; d="scan'208";a="593337468" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-iad-1e-m6i4x-6e7a78d7.us-east-1.amazon.com) ([10.43.8.6]) by smtp-border-fw-52002.iad7.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Nov 2023 14:36:00 +0000 Received: from smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev (iad7-ws-svc-p70-lb3-vlan2.iad.amazon.com [10.32.235.34]) by email-inbound-relay-iad-1e-m6i4x-6e7a78d7.us-east-1.amazon.com (Postfix) with ESMTPS id 354448463C; Mon, 6 Nov 2023 14:35:49 +0000 (UTC) Received: from EX19MTAUWA002.ant.amazon.com [10.0.38.20:33609] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.52.187:2525] with esmtp (Farcaster) id 17b942b6-4bce-4e6d-bd4d-69894513813a; Mon, 6 Nov 2023 14:35:49 +0000 (UTC) X-Farcaster-Flow-ID: 17b942b6-4bce-4e6d-bd4d-69894513813a Received: from EX19MTAUWB001.ant.amazon.com (10.250.64.248) by EX19MTAUWA002.ant.amazon.com (10.250.64.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.39; Mon, 6 Nov 2023 14:35:38 +0000 Received: from u3832b3a9db3152.ant.amazon.com (10.106.83.6) by mail-relay.amazon.com (10.250.64.254) with Microsoft SMTP Server id 15.2.1118.39 via Frontend Transport; Mon, 6 Nov 2023 14:35:35 +0000 From: David Woodhouse To: CC: Kevin Wolf , Hanna Reitz , Peter Maydell , Stefano Stabellini , Anthony Perard , Paul Durrant , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini , Richard Henderson , Eduardo Habkost , "Michael S. Tsirkin" , Marcel Apfelbaum , Jason Wang , Marcelo Tosatti , , , Subject: [PATCH v4 08/17] hw/xen: do not repeatedly try to create a failing backend device Date: Mon, 6 Nov 2023 14:34:58 +0000 Message-ID: <20231106143507.1060610-9-dwmw2@infradead.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231106143507.1060610-1-dwmw2@infradead.org> References: <20231106143507.1060610-1-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Precedence: Bulk 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 12ff782005..3ffd1a5333 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);