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=-5.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A8730C433DF for ; Fri, 16 Oct 2020 08:56:59 +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 2E55D20663 for ; Fri, 16 Oct 2020 08:56:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="tlCeww70" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E55D20663 Authentication-Results: mail.kernel.org; dmarc=fail (p=none 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.7842.20659 (Exim 4.92) (envelope-from ) id 1kTLXZ-0002hB-Il; Fri, 16 Oct 2020 08:56:45 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 7842.20659; Fri, 16 Oct 2020 08:56:45 +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" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kTLXZ-0002h4-Ex; Fri, 16 Oct 2020 08:56:45 +0000 Received: by outflank-mailman (input) for mailman id 7842; Fri, 16 Oct 2020 08:56:44 +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 1kTLXY-0002gv-6E for xen-devel@lists.xenproject.org; Fri, 16 Oct 2020 08:56:44 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id c96010d6-d6ae-44c4-b696-86114a01252d; Fri, 16 Oct 2020 08:56:43 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5006EAC0C; Fri, 16 Oct 2020 08:56:42 +0000 (UTC) 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 1kTLXY-0002gv-6E for xen-devel@lists.xenproject.org; Fri, 16 Oct 2020 08:56:44 +0000 X-Inumbo-ID: c96010d6-d6ae-44c4-b696-86114a01252d Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id c96010d6-d6ae-44c4-b696-86114a01252d; Fri, 16 Oct 2020 08:56:43 +0000 (UTC) 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=1602838602; h=from:from:reply-to:subject:subject: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=2dy94yMzztdQsQpIhT40xhT2ki5Jo8sjdCZ511fC+Pk=; b=tlCeww70D4k6vNbikgYBYG9T5lcdLE5LDlnr7/ldWGNVFpg0pb2ohCbScR+19FcPzANgOX 0V/ijDFM8lkuyAcx1E+Nwma1NxCBTesEgCQwz5qhoQMQNNj53ZfPcxH3SXcH/8Ly9zkdao W3HkbuJoycX8Um3SZGv86JDhtWSnICI= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5006EAC0C; Fri, 16 Oct 2020 08:56:42 +0000 (UTC) Subject: Re: [PATCH V2 21/23] xen/arm: Add mapcache invalidation handling To: Julien Grall Cc: Oleksandr Tyshchenko , xen-devel@lists.xenproject.org, Oleksandr Tyshchenko , Stefano Stabellini , Volodymyr Babchuk , Julien Grall References: <1602780274-29141-1-git-send-email-olekstysh@gmail.com> <1602780274-29141-22-git-send-email-olekstysh@gmail.com> From: Jan Beulich Message-ID: Date: Fri, 16 Oct 2020 10:56:43 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 16.10.2020 10:41, Julien Grall wrote: > On 16/10/2020 07:29, Jan Beulich wrote: >> Given how p2m_free_entry() works (or is supposed to work in the >> long run), is the new code you add guaranteed to only alter leaf >> entries? > > This path may also be called with tables. I think we want to move the > check in p2m_free_entry() so we can find the correct leaf type. > >> If not, the freeing of page tables needs deferring until >> after qemu has dropped its mappings. > > Freeing the page tables doesn't release a page. So may I ask why we > would need to defer it? Oh, sorry - qemu of course doesn't use the same p2m, so the intermediate page tables are private to the subject guest. >> And with there being refcounting only for foreign pages, how do >> you prevent the freeing of the page just unmapped before qemu has >> dropped its possible mapping? > QEMU mappings can only be done using the foreign mapping interface. This > means that page reference count will be incremented for each QEMU > mappings. Therefore the page cannot disappear until QEMU dropped the > last reference. Okay, sorry for the noise then. Jan