diff options
| -rw-r--r-- | content.tex | 11 | ||||
| -rw-r--r-- | packed-ring.tex | 2 |
2 files changed, 10 insertions, 3 deletions
diff --git a/content.tex b/content.tex index 68b7db0..979dbfc 100644 --- a/content.tex +++ b/content.tex @@ -786,7 +786,7 @@ struct virtio_pci_common_cfg { /* About a specific virtqueue. */ le16 queue_select; /* read-write */ - le16 queue_size; /* read-write, power of 2, or 0. */ + le16 queue_size; /* read-write */ le16 queue_msix_vector; /* read-write */ le16 queue_enable; /* read-write */ le16 queue_notify_off; /* read-only for driver */ @@ -903,11 +903,18 @@ The device MUST present a 0 in \field{queue_enable} on reset. The device MUST present a 0 in \field{queue_size} if the virtqueue corresponding to the current \field{queue_select} is unavailable. +If VIRTIO_F_RING_PACKED has not been negotiated, the device MUST +present either a value of 0 or a power of 2 in +\field{queue_size}. + \drivernormative{\paragraph}{Common configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Common configuration structure layout} The driver MUST NOT write to \field{device_feature}, \field{num_queues}, \field{config_generation} or \field{queue_notify_off}. -The driver MUST NOT write a value which is not a power of 2 to \field{queue_size}. +If VIRTIO_F_RING_PACKED has been negotiated, +the driver MUST NOT write the value 0 to \field{queue_size}. +If VIRTIO_F_RING_PACKED has not been negotiated, +the driver MUST NOT write a value which is not a power of 2 to \field{queue_size}. The driver MUST configure the other virtqueue fields before enabling the virtqueue with \field{queue_enable}. diff --git a/packed-ring.tex b/packed-ring.tex index f24f49b..2a6c685 100644 --- a/packed-ring.tex +++ b/packed-ring.tex @@ -386,7 +386,7 @@ part of the virtqueue. Queue Size corresponds to the maximum number of descriptors in the virtqueue\footnote{For example, if Queue Size is 4 then at most 4 buffers can be queued at any given time.}. The Queue Size value does not -have to be a power of 2 unless enforced by the transport. +have to be a power of 2. \drivernormative{\subsection}{Virtqueues}{Basic Facilities of a Virtio Device / Packed Virtqueues} |