diff options
| -rw-r--r-- | content.tex | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/content.tex b/content.tex index 222b78e..e57ebc5 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 these 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 +5838,22 @@ 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 SHOULD accept VIRTIO_F_IOMMU_PLATFORM if it is offered, and it MUST +then either disable the IOMMU or configure the IOMMU to translate bus addresses +passed to the device into physical addresses in memory. If +VIRTIO_F_IOMMU_PLATFORM is not offered, then a driver MUST pass only physical +addresses to the device. + \devicenormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} A device MUST offer VIRTIO_F_VERSION_1. A device MAY fail to operate further if VIRTIO_F_VERSION_1 is not accepted. +A device SHOULD offer VIRTIO_F_IOMMU_PLATFORM if it is behind an IOMMU that +translates bus addresses from the device into physical addresses in memory. +A device MAY fail to operate further if VIRTIO_F_IOMMU_PLATFORM is not +accepted. + \section{Legacy Interface: Reserved Feature Bits}\label{sec:Reserved Feature Bits / Legacy Interface: Reserved Feature Bits} Transitional devices MAY offer the following: |