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=-7.3 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 0A89DC433DB for ; Mon, 11 Jan 2021 15:21:21 +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 A570D225AC for ; Mon, 11 Jan 2021 15:21:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A570D225AC 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.64956.114918 (Exim 4.92) (envelope-from ) id 1kyz0K-0003tu-Uh; Mon, 11 Jan 2021 15:21:12 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 64956.114918; Mon, 11 Jan 2021 15:21:12 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kyz0K-0003tn-RV; Mon, 11 Jan 2021 15:21:12 +0000 Received: by outflank-mailman (input) for mailman id 64956; Mon, 11 Jan 2021 15:21:11 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kyz0J-0003tS-Iu for xen-devel@lists.xenproject.org; Mon, 11 Jan 2021 15:21:11 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 9f0683d8-72de-4646-9df8-79ff426438e7; Mon, 11 Jan 2021 15:21:09 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0E76FAB7A; Mon, 11 Jan 2021 15:21:09 +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: 9f0683d8-72de-4646-9df8-79ff426438e7 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=1610378469; 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=BiTouGOI4Hcfhh1Fi5gzm+6cCWiXp5e/O9CJgyTYhh8=; b=HVqtEl1vjgynM8DQteT5s8WjenVwutBQUjEooxKOfhLR7bNBTmcryW6s7R94pLMKwhjdX9 G9ZtDnmA5PHRKgiBVBjXb4eE7bDRCBa2bRgKq16pW6btu27n2r1Xf90pqnOX9v7xUOWfA9 c7rK1cdWbvSRO9voFFerq2ml/CIzC78= Subject: Re: [PATCH] hvmloader: pass PCI MMIO layout to OVMF as an info table To: Laszlo Ersek Cc: andrew.cooper3@citrix.com, roger.pau@citrix.com, wl@xen.org, iwj@xenproject.org, anthony.perard@citrix.com, xen-devel@lists.xenproject.org, Igor Druzhinin References: <1610340812-24397-1-git-send-email-igor.druzhinin@citrix.com> <20b1fe43-370b-9afc-6938-379480908578@redhat.com> From: Jan Beulich Message-ID: Date: Mon, 11 Jan 2021 16:21:08 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20b1fe43-370b-9afc-6938-379480908578@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 11.01.2021 15:49, Laszlo Ersek wrote: > On 01/11/21 15:00, Igor Druzhinin wrote: >> On 11/01/2021 09:27, Jan Beulich wrote: >>> On 11.01.2021 05:53, Igor Druzhinin wrote: >>>> We faced a problem with passing through a PCI device with 64GB BAR to >>>> UEFI guest. The BAR is expectedly programmed into 64-bit PCI aperture at >>>> 64G address which pushes physical address space to 37 bits. OVMF uses >>>> address width early in PEI phase to make DXE identity pages covering >>>> the whole addressable space so it needs to know the last address it needs >>>> to cover but at the same time not overdo the mappings. >>>> >>>> As there is seemingly no other way to pass or get this information in >>>> OVMF at this early phase (ACPI is not yet available, PCI is not yet enumerated, >>>> xenstore is not yet initialized) - extend the info structure with a new >>>> table. Since the structure was initially created to be extendable - >>>> the change is backward compatible. >>> >>> How does UEFI handle the same situation on baremetal? I'd guess it is >>> in even more trouble there, as it couldn't even read addresses from >>> BARs, but would first need to assign them (or at least calculate >>> their intended positions). >> >> Maybe Laszlo or Anthony could answer this question quickly while I'm investigating? > > On the bare metal, the phys address width of the processor is known. >From CPUID I suppose. > OVMF does the whole calculation in reverse because there's no way for it > to know the physical address width of the physical (= host) CPU. > "Overdoing" the mappings doesn't only waste resources, it breaks hard > with EPT -- access to a GPA that is inexpressible with the phys address > width of the host CPU (= not mappable successfully with the nested page > tables) will behave super bad. I don't recall the exact symptoms, but it > prevents booting the guest OS. > > This is why the most conservative 36-bit width is assumed by default. IOW you don't trust virtualized CPUID output? Jan