[PATCH v3] content: document SR-IOV driver requirements

[Tiwei Bie <tiwei.bie@intel.com>]

Document the driver requirements for the VIRTIO_F_SR_IOV
feature bit.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/13
---
v2:
- Fix the commit message (MST);
- Improve the wording (MST);
- Drop unnecessary parts (MST);

v3:
- status -> device status (MST);

 content.tex | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/content.tex b/content.tex
index be18234..ab18210 100644
--- a/content.tex
+++ b/content.tex
@@ -5387,6 +5387,21 @@ A driver SHOULD accept VIRTIO_F_IO_BARRIER if it is offered.
 If VIRTIO_F_IO_BARRIER has been negotiated, a driver MUST use
 the barriers suitable for hardware devices.
 
+If VIRTIO_F_SR_IOV has been negotiated, a driver MAY enable
+virtual functions through the device's PCI SR-IOV capability
+structure.  A driver MUST NOT negotiate VIRTIO_F_SR_IOV if
+the device does not have a PCI SR-IOV capability structure
+or is not a PCI device.  A driver MUST negotiate
+VIRTIO_F_SR_IOV and complete the feature negotiation
+(including checking the FEATURES_OK \field{device status}
+bit) before enabling virtual functions through the device's
+PCI SR-IOV capability structure.  After once successfully
+negotiating VIRTIO_F_SR_IOV, the driver MAY enable virtual
+functions through the device's PCI SR-IOV capability
+structure even if the device or the system has been fully
+or partially reset, and even without re-negotiating
+VIRTIO_F_SR_IOV after the reset.
+
 \devicenormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
 
 A device MUST offer VIRTIO_F_VERSION_1.  A device MAY fail to operate further
-- 
2.17.0