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Subject: Re: [virtio-dev] [PATCH] split-ring: Demand that a device must not change descriptor entries
On 11.11.19 18:17, Rob Miller wrote:
what is trying to be solvedÂhere? There is a reason why this is allowed as some vendors update the table when using RX_MERABLE_BUFFERs & F_IN_ORDER features
OK, good to know. Which fields are updated then? Under which conditions (ie. in which states of the device)?
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...
Jan
Rob Miller rob.miller@broadcom.com <mailto:rob.miller@broadcom.com> (919)721-3339On Mon, Nov 11, 2019 at 12:13 PM Jan Kiszka <jan.kiszka@siemens.com <mailto:jan.kiszka@siemens.com>> wrote:From: Jan Kiszka <jan.kiszka@siemens.com <mailto:jan.kiszka@siemens.com>> 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. See also https://lists.oasis-open.org/archives/virtio-dev/201910/msg00057.html. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com <mailto:jan.kiszka@siemens.com>> --- Âsplit-ring.tex | 2 +- Â1 file changed, 1 insertion(+), 1 deletion(-) 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 Â\devicenormative{\subsubsection}{The Virtqueue Descriptor Table}{Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Descriptor Table} ÂA device MUST NOT write to a device-readable buffer, and a device SHOULD NOT Âread a device-writable buffer (it MAY do so for debugging or diagnostic -purposes). +purposes). A device MUST NOT write to any descriptor table entry. Â\drivernormative{\subsubsection}{The Virtqueue Descriptor Table}{Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Descriptor Table} ÂDrivers MUST NOT add a descriptor chain longer than $2^{32}$ bytes in total;-- 2.16.4--------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org <mailto:virtio-dev-unsubscribe@lists.oasis-open.org> For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org <mailto:virtio-dev-help@lists.oasis-open.org>
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