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| -rw-r--r-- | content.tex | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/content.tex b/content.tex index 797e8f2..d68511a 100644 --- a/content.tex +++ b/content.tex @@ -1329,12 +1329,28 @@ driver attempts to drive them: of BAR0 by presenting zeroes on every BAR and ignoring writes. \end{enumerate} -\paragraph{Queue Vector Configuration}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Queue Vector Configuration} +\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 (through standard PCI configuration space) \field{config_msix_vector} and \field{queue_msix_vector} are used to map configuration change and queue interrupts to MSI-X vectors. In this case, the ISR Status is unused. +A device that has an MSI-X capability SHOULD support at least 2 +and at most 0x800 MSI-X vectors. +Device MUST report the number of vectors supported in +\field{Table Size} in the MSI-X Capability as specified in +\hyperref[intro:PCI]{[PCI]}. +Driver MUST support device with any MSI-X Table Size 0 to 0x7FF. +Driver MAY fall back on using INT\#x interrupts for a device +which only supports one MSI-X vector (MSI-X Table Size = 0). + +Driver MAY intepret the Table Size as a hint from the device +for the suggested number of MSI-X vectors to use. +Therefore, devices SHOULD restrict the reported MSI-X Table Size field +to a value that might benefit system performance. +For example, a device which does not expect to send +interrupts at a high rate might only specify 2 MSI-X vectors. + Writing a valid MSI-X Table entry number, 0 to 0x7FF, to \field{config_msix_vector}/\field{queue_msix_vector} maps interrupts triggered by the configuration change/selected queue events respectively to @@ -1347,6 +1363,13 @@ value: #define VIRTIO_MSI_NO_VECTOR 0xffff \end{lstlisting} +Driver MUST NOT attempt to map an event to a vector +outside the MSI-X Table supported by the device, +as reported by \field{Table Size} in the MSI-X Capability. +Device MUST support mapping any event type to any valid +vector 0 to MSI-X \field{Table Size}. +Device MUST support unmapping any event type. + Reading these registers returns vector mapped to a given event, or NO_VECTOR if unmapped. All queue and configuration change events are unmapped by default. @@ -1361,6 +1384,10 @@ failure, NO_VECTOR is returned. If a mapping failure is detected, the driver MAY retry mapping with fewer vectors, disable MSI-X or report device failure. +Devices SHOULD NOT cause mapping an event to vector to fail +unless it is impossible for the device to satisfy the mapping +request. + \paragraph{Virtqueue Configuration}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtqueue Configuration} As a device can have zero or more virtqueues for bulk data |