From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-6798-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id EA8F6985E3D for ; Thu, 27 Feb 2020 10:05:58 +0000 (UTC) Date: Thu, 27 Feb 2020 05:05:46 -0500 From: "Michael S. Tsirkin" Message-ID: <20200227050257-mutt-send-email-mst@kernel.org> References: <4fa78a91-751d-a7b5-fadf-b0ae8a5d5903@siemens.com> <2fed2342-d6fa-17ff-a812-ec01a14d8183@siemens.com> MIME-Version: 1.0 In-Reply-To: <2fed2342-d6fa-17ff-a812-ec01a14d8183@siemens.com> Subject: Re: [virtio-dev] [PATCH] split-ring: Demand that a device must not change descriptor entries Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline To: Jan Kiszka Cc: Rob Miller , "virtio-dev@lists.oasis-open.org" List-ID: On Mon, Nov 11, 2019 at 06:26:58PM +0100, Jan Kiszka wrote: > On 11.11.19 18:17, Rob Miller wrote: > > what is trying to be solved=A0here? There is a reason why this is allow= ed > > as some vendors update the table when using RX_MERABLE_BUFFERs & > > F_IN_ORDER features >=20 > OK, good to know. Which fields are updated then? Under which conditions (= ie. > in which states of the device)? >=20 > The background is in the link below. My goal was to find a simple way > declaring all fields read-only for the device to avoid problems with new > implementations. But it looks like it's more complicated... >=20 > Jan No answer yet. Rob I see the following options: - proceed with the ballot as is ignoring your comment. Maybe it's all a misunderstanding? It could be the comment was referring to the packed ring, where this patch refers to the split ring. - make it weaker: MUST if PLATFORM_ACCESS is negotiated, and SHOULD if it isn't. > >=20 > > Rob Miller > > rob.miller@broadcom.com > > (919)721-3339 > >=20 > >=20 > > On Mon, Nov 11, 2019 at 12:13 PM Jan Kiszka > > wrote: > >=20 > > From: Jan Kiszka > > > >=20 > > So far the spec only indirectly says that a descriptor table entry = is > > not modified by a device when processing it. Make this explicit by > > adding it as normative requirement. Existing drivers already depend= on > > this. > >=20 > > See also > > https://lists.oasis-open.org/archives/virtio-dev/201910/msg00057.ht= ml. > >=20 > > Signed-off-by: Jan Kiszka > > > > --- > > =A0split-ring.tex | 2 +- > > =A01 file changed, 1 insertion(+), 1 deletion(-) > >=20 > > diff --git a/split-ring.tex b/split-ring.tex > > index 123ac9f..bfef62d 100644 > > --- a/split-ring.tex > > +++ b/split-ring.tex > > @@ -217,7 +217,7 @@ \subsection{The Virtqueue Descriptor > > Table}\label{sec:Basic Facilities of a Virt > > =A0\devicenormative{\subsubsection}{The Virtqueue Descriptor > > Table}{Basic Facilities of a Virtio Device / Virtqueues / The > > Virtqueue Descriptor Table} > > =A0A device MUST NOT write to a device-readable buffer, and a devi= ce > > SHOULD NOT > > =A0read a device-writable buffer (it MAY do so for debugging or > > diagnostic > > -purposes). > > +purposes). A device MUST NOT write to any descriptor table entry. > >=20 > > =A0\drivernormative{\subsubsection}{The Virtqueue Descriptor > > Table}{Basic Facilities of a Virtio Device / Virtqueues / The > > Virtqueue Descriptor Table} > > =A0Drivers MUST NOT add a descriptor chain longer than $2^{32}$ by= tes > > in total; > > -- 2.16.4 > >=20 > > -------------------------------------------------------------------= -- > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > > > For additional commands, e-mail: > > virtio-dev-help@lists.oasis-open.org > > > >=20 >=20 > --=20 > Siemens AG, Corporate Technology, CT RDA IOT SES-DE > Corporate Competence Center Embedded Linux >=20 > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org