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Subject: Re: [PATCH] context: Document VIRTIO_F_IOMMU_PLATFORM reserved feature bit (33)
On Thu, Oct 20, 2016 at 07:54:30PM +0300, Michael S. Tsirkin wrote: > On Tue, Oct 11, 2016 at 01:51:32PM +0100, Will Deacon wrote: > > diff --git a/content.tex b/content.tex > > index 222b78e7f5d8..1240d0005d77 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -95,10 +95,10 @@ Feature bits are allocated as follows: > > \begin{description} > > \item[0 to 23] Feature bits for the specific device type > > > > -\item[24 to 32] Feature bits reserved for extensions to the queue and > > +\item[24 to 33] Feature bits reserved for extensions to the queue and > > feature negotiation mechanisms > > > > -\item[33 and above] Feature bits reserved for future extensions. > > +\item[34 and above] Feature bits reserved for future extensions. > > \end{description} > > > > \begin{note} > > @@ -5813,7 +5813,7 @@ descriptor for the \field{sense_len}, \field{residual}, > > > > \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} > > > > -Currently there are three device-independent feature bits defined: > > +Currently there are four device-independent feature bits defined: > > > > \begin{description} > > \item[VIRTIO_F_RING_INDIRECT_DESC (28)] Negotiating this feature indicates > > @@ -5825,6 +5825,12 @@ Currently there are three device-independent feature bits defined: > > > > \item[VIRTIO_F_VERSION_1(32)] This indicates compliance with this > > specification, giving a simple way to detect legacy devices or drivers. > > + > > + \item[VIRTIO_F_IOMMU_PLATFORM(33)] This feature indicates that the device is > > + behind an IOMMU that translates bus addresses from the device into physical > > + addresses in memory. If this feature bit is set to 0, then the device emits > > + physical addresses which are not translated further, even though an IOMMU > > + may be present. > > \end{description} > > > > \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} > > @@ -5832,11 +5838,21 @@ Currently there are three device-independent feature bits defined: > > A driver MUST accept VIRTIO_F_VERSION_1 if it is offered. A driver > > MAY fail to operate further if VIRTIO_F_VERSION_1 is not offered. > > > > +A driver MUST accept VIRTIO_F_IOMMU_PLATFORM if it is offered, > > I would make it a SHOULD, we can't really add requirements > that make existing confirmant drivers non-confirmant. > > > and it MUST then > > .. either disable the IOMMU or .. Okey doke, with that qualification then this sounds good to me. I'll spin a v2 with these changes and the other suggestion from Stefan. Cheers for the review, Will
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