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| -rw-r--r-- | content.tex | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/content.tex b/content.tex index 2aa3aac..be9f176 100644 --- a/content.tex +++ b/content.tex @@ -1295,6 +1295,20 @@ As a prerequisite to device initialization, the driver scans the PCI capability list, detecting virtio configuration layout using Virtio Structure PCI capabilities. +\paragraph{Non-transitional Device With Legacy Driver}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Non-transitional Device With Legacy Driver} + +Non-transitional devices, on a platform where a legacy driver for +a legacy device with the same ID might have previously existed, +MUST take the following steps to fail gracefully when a legacy +driver attempts to drive them: + +\begin{enumerate} +\item Present an I/O BAR in BAR0, and +\item Respond to a single-byte zero write to offset 18 + (corresponding to Device Status register in the legacy layout) + of BAR0 by presenting zeroes on every BAR and ignoring writes. +\end{enumerate} + \subparagraph{Legacy Interface: A Note on Device Layout Detection}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtio Device Configuration Layout Detection / Legacy Interface: A Note on Device Layout Detection} Legacy drivers skipped the Device Layout Detection step, assuming legacy @@ -1317,18 +1331,6 @@ Capabilities on the capability list. If these are not present, driver should assume a legacy device, and fail gracefully. -Non-transitional devices, on a platform where a legacy driver for -a legacy device with the same ID might have previously existed, -MUST take the following steps to fail gracefully when a legacy -driver attempts to drive them: - -\begin{enumerate} -\item Present an I/O BAR in BAR0, and -\item Respond to a single-byte zero write to offset 18 - (corresponding to Device Status register in the legacy layout) - of BAR0 by presenting zeroes on every BAR and ignoring writes. -\end{enumerate} - \paragraph{MSI-X Vector Configuration}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / MSI-X Vector Configuration} When MSI-X capability is present and enabled in the device |