From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 181D320958BDA for ; Wed, 6 Sep 2017 01:08:15 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5C27A356C9; Wed, 6 Sep 2017 08:11:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 5C27A356C9 Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=lersek@redhat.com Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-41.rdu2.redhat.com [10.10.120.41]) by smtp.corp.redhat.com (Postfix) with ESMTP id ED72119CAE; Wed, 6 Sep 2017 08:11:02 +0000 (UTC) From: Laszlo Ersek To: Brijesh Singh , edk2-devel@lists.01.org Cc: Jordan Justen , Ard Biesheuvel , Tom Lendacky References: <1504265045-19008-1-git-send-email-brijesh.singh@amd.com> <1504265045-19008-5-git-send-email-brijesh.singh@amd.com> <09699a1f-9bc9-02d1-f7d0-99cd9d42051e@redhat.com> Message-ID: Date: Wed, 6 Sep 2017 10:11:01 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <09699a1f-9bc9-02d1-f7d0-99cd9d42051e@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 06 Sep 2017 08:11:04 +0000 (UTC) Subject: Re: [PATCH 4/5] OvmfPkg/VirtioNetDxe: map virtio-net transmit request buffer X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Sep 2017 08:08:15 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 09/05/17 14:41, Laszlo Ersek wrote: > On 09/01/17 13:24, Brijesh Singh wrote: >> When device is behind the IOMMU, driver is require to pass the device >> address of transmit buffer for the bus master operations. >> >> The patch uses VirtioMapAllBytesInSharedBuffer() to map transmit buffer >> system physical address to the device address. >> >> Since the transmit buffers are returned back to caller in >> VirtioNetGetStatus() hence we use OrderCollection library interface to >> save the host to device address mapping. After the buffer is succesfully >> transmited we do reverse lookup in OrderCollection data structure to get >> the host address for the transmitted device address. >> >> Cc: Ard Biesheuvel >> Cc: Jordan Justen >> Cc: Tom Lendacky >> Cc: Laszlo Ersek >> Contributed-under: TianoCore Contribution Agreement 1.1 >> Signed-off-by: Brijesh Singh >> --- >> OvmfPkg/VirtioNetDxe/VirtioNet.inf | 1 + >> OvmfPkg/VirtioNetDxe/VirtioNet.h | 19 +++ >> OvmfPkg/VirtioNetDxe/SnpGetStatus.c | 30 +++- >> OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c | 157 ++++++++++++++++++++ >> OvmfPkg/VirtioNetDxe/SnpTransmit.c | 37 ++++- >> 5 files changed, 232 insertions(+), 12 deletions(-) > (7) We'll have to document the new model in "TechNotes.txt". I've now re-read the final section of the text file, section Virtio internals -- Tx I propose the following updates. (Here I'm providing a diff, not a desired "end status", like I did for the diagram earlier. A diff is harder to interpret for a diagram, but easy for plain text.) Please verify that the proposed documentation updates match the logic that you've implemented: > diff --git a/OvmfPkg/VirtioNetDxe/TechNotes.txt b/OvmfPkg/VirtioNetDxe/TechNotes.txt > index 9c1dfe6a773e..7a7b3071abba 100644 > --- a/OvmfPkg/VirtioNetDxe/TechNotes.txt > +++ b/OvmfPkg/VirtioNetDxe/TechNotes.txt > @@ -310,10 +310,14 @@ in the following: > that is shared by all of the head descriptors. This virtio-net request header > is never modified by the host. > > -- Each tail descriptor is re-pointed to the caller-supplied packet buffer > - whenever VirtioNetTransmit places the corresponding head descriptor on the > - Available Ring. The caller is responsible to hang on to the unmodified buffer > - until it is reported transmitted by VirtioNetGetStatus. > +- Each tail descriptor is re-pointed to the device-mapped address of the > + caller-supplied packet buffer whenever VirtioNetTransmit places the > + corresponding head descriptor on the Available Ring. A reverse mapping, from > + the device-mapped address to the caller-supplied packet address, is saved in > + an associative data structure that belongs to the driver instance. > + > +- Per spec, the caller is responsible to hang on to the unmodified packet > + buffer until it is reported transmitted by VirtioNetGetStatus. > > Steps of packet transmission: > > @@ -336,9 +340,11 @@ Steps of packet transmission: > - Client code calls VirtioNetGetStatus. In case the Used Ring is empty, the > function reports no Tx completion. Otherwise, a head descriptor's index is > consumed from the Used Ring and recycled to the private stack. The client > - code's original packet buffer address is fetched from the tail descriptor > - (where it has been stored at VirtioNetTransmit time) and returned to the > - caller. > + code's original packet buffer address is calculated by fetching the > + device-mapped address from the tail descriptor (where it has been stored at > + VirtioNetTransmit time), and by looking up the device-mapped address in the > + associative data structure. The reverse-mapped packet buffer address is > + returned to the caller. > > - The Len field of the Used Ring Element is not checked. The host is assumed to > have transmitted the entire packet -- VirtioNetTransmit had forced it below Thanks! Laszlo