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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,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 1A931C433E0 for ; Wed, 5 Aug 2020 16:42:11 +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 DD3C32067D for ; Wed, 5 Aug 2020 16:42:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="y22tqEcv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DD3C32067D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k3MUK-0000eU-LW; Wed, 05 Aug 2020 16:42:00 +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 1k3MUJ-0000eL-9E for xen-devel@lists.xenproject.org; Wed, 05 Aug 2020 16:41:59 +0000 X-Inumbo-ID: e4ffa99b-04ae-4d85-9e99-3dae58643633 Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id e4ffa99b-04ae-4d85-9e99-3dae58643633; Wed, 05 Aug 2020 16:41:58 +0000 (UTC) Received: from localhost (c-67-164-102-47.hsd1.ca.comcast.net [67.164.102.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 55BC82067D; Wed, 5 Aug 2020 16:41:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596645717; bh=kQSllmn6YanvKxFLx6/+6zwojR89djKhoceBz2aAjyY=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=y22tqEcv4kHr3qJFIZ3SklKLXa5g2UJ1OKBUk8ZkdLgyuyQdtIssWTYW+fDgpCj7R rF0mUHH+XnET6R7YrJqJZMvrknYQsyUPl4thfD2Lc59ZVE6FoeR+Thz2a/fL6X4yWg IO1LujMZLdl3HM5nWD5+qyYJ1VVOlIhNrYzeejJo= Date: Wed, 5 Aug 2020 09:41:56 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-T480s To: Jan Beulich Subject: Re: [RFC PATCH V1 04/12] xen/arm: Introduce arch specific bits for IOREQ/DM features In-Reply-To: Message-ID: References: <1596478888-23030-1-git-send-email-olekstysh@gmail.com> <1596478888-23030-5-git-send-email-olekstysh@gmail.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Julien Grall , Wei Liu , Andrew Cooper , Ian Jackson , George Dunlap , Oleksandr Tyshchenko , Oleksandr Tyshchenko , Julien Grall , xen-devel@lists.xenproject.org, Daniel De Graaf , Volodymyr Babchuk Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On Wed, 5 Aug 2020, Jan Beulich wrote: > On 05.08.2020 01:22, Stefano Stabellini wrote: > > On Mon, 3 Aug 2020, Oleksandr Tyshchenko wrote: > >> --- a/xen/include/asm-arm/p2m.h > >> +++ b/xen/include/asm-arm/p2m.h > >> @@ -385,10 +385,11 @@ static inline int set_foreign_p2m_entry(struct domain *d, unsigned long gfn, > >> mfn_t mfn) > >> { > >> /* > >> - * NOTE: If this is implemented then proper reference counting of > >> - * foreign entries will need to be implemented. > >> + * XXX: handle properly reference. It looks like the page may not always > >> + * belong to d. > > > > Just as a reference, and without taking away anything from the comment, > > I think that QEMU is doing its own internal reference counting for these > > mappings. > > Which of course in no way replaces the need to do proper ref counting > in Xen. (Just FAOD, as I'm not sure why you've said what you've said.) Given the state of the series, which is a RFC, I only meant to say that the lack of refcounting shouldn't prevent things from working when using QEMU. In the sense that if somebody wants to give it a try for an early demo, they should be able to see it running without crashes. Of course, refcounting needs to be implemented.