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 X-Spam-Level: X-Spam-Status: No, score=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23978C433B4 for ; Thu, 29 Apr 2021 09:31:30 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id B73826143F for ; Thu, 29 Apr 2021 09:31:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B73826143F Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.119836.226562 (Exim 4.92) (envelope-from ) id 1lc30v-0005If-Kt; Thu, 29 Apr 2021 09:31:17 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 119836.226562; Thu, 29 Apr 2021 09:31:17 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lc30v-0005IY-Hj; Thu, 29 Apr 2021 09:31:17 +0000 Received: by outflank-mailman (input) for mailman id 119836; Thu, 29 Apr 2021 09:31:15 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lc30t-0005IA-TP for xen-devel@lists.xenproject.org; Thu, 29 Apr 2021 09:31:15 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id daf7eead-c94e-4af9-aea9-f483e61b1c38; Thu, 29 Apr 2021 09:31:10 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3BA10B004; Thu, 29 Apr 2021 09:31:09 +0000 (UTC) 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: daf7eead-c94e-4af9-aea9-f483e61b1c38 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1619688669; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oAekxrxornC8EWfdiuAI1iWCTS4Ircvg83KybkTn3k8=; b=dO2PY+4Hj1nUgvHnzWwBU6IXA2Mr4eekbaQ9tRQdJ9HIJq/ZngLak+DmhOWgDxb/HoLO0r GYAesu49/40OE0lNVOEM9rDlqSobD8nEf3IkXWpUo0QfYIsa12lYCP28LcLhASAZfbDblU JyzHTJwBJEPBR0rWZcb6PhsIQyQxSeY= Subject: Ping: [PATCH v3] gnttab: defer allocation of status frame tracking array From: Jan Beulich To: Andrew Cooper , Julien Grall Cc: George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , "xen-devel@lists.xenproject.org" References: Message-ID: Date: Thu, 29 Apr 2021 11:31:08 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 15.04.2021 11:41, Jan Beulich wrote: > This array can be large when many grant frames are permitted; avoid > allocating it when it's not going to be used anyway, by doing this only > in gnttab_populate_status_frames(). > > Signed-off-by: Jan Beulich I know there has been controversy here. Julien - you seemed to agree, and iirc you partly drove how the patch is looking now. May I ask for an ack? Andrew - you disagreed for reasons that neither Julien nor I could really understand. Would you firmly nack the change and suggest a way out, or would you allow this to go in with someone else's ack? Thanks, Jan > --- > v3: Drop smp_wmb(). Re-base. > v2: Defer allocation to when a domain actually switches to the v2 grant > API. > > --- a/xen/common/grant_table.c > +++ b/xen/common/grant_table.c > @@ -1747,6 +1747,17 @@ gnttab_populate_status_frames(struct dom > /* Make sure, prior version checks are architectural visible */ > block_speculation(); > > + if ( gt->status == ZERO_BLOCK_PTR ) > + { > + gt->status = xzalloc_array(grant_status_t *, > + grant_to_status_frames(gt->max_grant_frames)); > + if ( !gt->status ) > + { > + gt->status = ZERO_BLOCK_PTR; > + return -ENOMEM; > + } > + } > + > for ( i = nr_status_frames(gt); i < req_status_frames; i++ ) > { > if ( (gt->status[i] = alloc_xenheap_page()) == NULL ) > @@ -1767,18 +1778,23 @@ status_alloc_failed: > free_xenheap_page(gt->status[i]); > gt->status[i] = NULL; > } > + if ( !nr_status_frames(gt) ) > + { > + xfree(gt->status); > + gt->status = ZERO_BLOCK_PTR; > + } > return -ENOMEM; > } > > static int > gnttab_unpopulate_status_frames(struct domain *d, struct grant_table *gt) > { > - unsigned int i; > + unsigned int i, n = nr_status_frames(gt); > > /* Make sure, prior version checks are architectural visible */ > block_speculation(); > > - for ( i = 0; i < nr_status_frames(gt); i++ ) > + for ( i = 0; i < n; i++ ) > { > struct page_info *pg = virt_to_page(gt->status[i]); > gfn_t gfn = gnttab_get_frame_gfn(gt, true, i); > @@ -1833,12 +1849,11 @@ gnttab_unpopulate_status_frames(struct d > page_set_owner(pg, NULL); > } > > - for ( i = 0; i < nr_status_frames(gt); i++ ) > - { > - free_xenheap_page(gt->status[i]); > - gt->status[i] = NULL; > - } > gt->nr_status_frames = 0; > + for ( i = 0; i < n; i++ ) > + free_xenheap_page(gt->status[i]); > + xfree(gt->status); > + gt->status = ZERO_BLOCK_PTR; > > return 0; > } > @@ -1969,11 +1984,11 @@ int grant_table_init(struct domain *d, i > if ( gt->shared_raw == NULL ) > goto out; > > - /* Status pages for grant table - for version 2 */ > - gt->status = xzalloc_array(grant_status_t *, > - grant_to_status_frames(gt->max_grant_frames)); > - if ( gt->status == NULL ) > - goto out; > + /* > + * Status page tracking array for v2 gets allocated on demand. But don't > + * leave a NULL pointer there. > + */ > + gt->status = ZERO_BLOCK_PTR; > > grant_write_lock(gt); > > @@ -4047,11 +4062,12 @@ int gnttab_acquire_resource( > if ( gt->gt_version != 2 ) > break; > > + rc = gnttab_get_status_frame_mfn(d, final_frame, &tmp); > + > /* Check that void ** is a suitable representation for gt->status. */ > BUILD_BUG_ON(!__builtin_types_compatible_p( > typeof(gt->status), grant_status_t **)); > vaddrs = (void **)gt->status; > - rc = gnttab_get_status_frame_mfn(d, final_frame, &tmp); > break; > } > >