From patchwork Wed Mar 16 16:10:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 12782916 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 2E95AC43217 for ; Wed, 16 Mar 2022 16:10:54 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.291212.494142 (Exim 4.92) (envelope-from ) id 1nUWEV-0000W6-Nk; Wed, 16 Mar 2022 16:10:43 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 291212.494142; Wed, 16 Mar 2022 16:10:43 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nUWEV-0000Uh-Gy; Wed, 16 Mar 2022 16:10:43 +0000 Received: by outflank-mailman (input) for mailman id 291212; Wed, 16 Mar 2022 16:10:42 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nUWEU-0000RR-Qb for xen-devel@lists.xenproject.org; Wed, 16 Mar 2022 16:10:42 +0000 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 93cf928a-a543-11ec-8eba-a37418f5ba1a; Wed, 16 Mar 2022 17:10:39 +0100 (CET) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 077BF21108; Wed, 16 Mar 2022 16:10:20 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id C0A3F139B5; Wed, 16 Mar 2022 16:10:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id rnCsLesLMmK2OwAAMHmgww (envelope-from ); Wed, 16 Mar 2022 16:10:19 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 93cf928a-a543-11ec-8eba-a37418f5ba1a DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1647447020; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=hZKD0EuTc6WQXVOTuJxQoolqoYXnAFSSnw7fgb9wYmQ=; b=VZ+kkIbd02t4dK03Jr3BAxZ/CFOFjXOwUiEyKhermAHZjL5tgRYuCm+Jlsn92Otc/2ipr7 N3An5DNKRI2mpzmrokc+l2budEABb3TgTefk64HzcMu+Igt+PtvVavhevb9mSPvZWLIpaj 5kr4QyUiueHc+quGGm7WoCqhK5I1TQU= From: Juergen Gross To: xen-devel@lists.xenproject.org Cc: Juergen Gross , Andrew Cooper , George Dunlap , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu Subject: [PATCH 0/3] tools/xenstore: add some new features to the documentation Date: Wed, 16 Mar 2022 17:10:14 +0100 Message-Id: <20220316161017.3579-1-jgross@suse.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 In the past there have been spotted some shortcomings in the Xenstore interface, which should be repaired. Those are in detail: - Using driver domains for large number of domains needs per domain Xenstore quota [1]. The feedback sent was rather slim (one reply), but it was preferring a new set of wire commands. - XSA-349 [2] has shown that the current definition of watches is not optimal, as it will trigger lots of events when a single one would suffice: for detecting new backend devices the backends in the Linux kernel are registering a watch for e.g. "/local/domain/0/backend" which will fire for ANY sub-node written below this node (on a test machine this added up to 91 watch events for only 3 devices). This can be limited dramatically by extending the XS_WATCH command to take another optional parameter specifying the depth of subdirectories to be considered for sending watch events ("0" would trigger a watch event only if the watched node itself being written). - New features like above being added might make migration of guests between hosts with different Xenstore variants harder, so it should be possible to set the available feature set per domain. For socket connections it should be possible to read the available features. - The special watches @introduceDomain and @releaseDomain are rather cumbersome to use, as they only tell you that SOME domain has been introduced/released. Any consumer of those watches needs to scan all domains on the host in order to find out the domid, causing significant pressure on the dominfo hypercall (imagine a system with 1000 domains running and one domain dying - there will be more than 1000 watch events triggered and 1000 xl daemons will try to find out whether "their" domain has died). Those watches should be enhanced to optionally be specific to a single domain and to let the event carry the related domid. As some of those extensions will need to be considered in the Xenstore migration stream, they should be defined in one go (in fact the 4th one wouldn't need that, but it can easily be connected to the 2nd one). As such extensions need to be flagged in the "features" in the ring page anyway, it is fine to implement them independently. Add the documentation of the new commands/features. [1]: https://lists.xen.org/archives/html/xen-devel/2020-06/msg00291.html [2]: http://xenbits.xen.org/xsa/advisory-349.html Juergen Gross (3): tools/xenstore: add documentation for new set/get-feature commands tools/xenstore: add documentation for new set/get-quota commands tools/xenstore: add documentation for extended watch command docs/misc/xenstore-ring.txt | 3 +++ docs/misc/xenstore.txt | 40 ++++++++++++++++++++++++++++++++++--- 2 files changed, 40 insertions(+), 3 deletions(-)