The last sub-engine of the XIVE architecture is the Interrupt
Virtualization Presentation Engine (IVPE). On HW, the IVRE and the
IVPE share elements, the Power Bus interface (CQ), the routing table
descriptors, and they can be combined in the same HW logic. We do the
same in QEMU and combine both engines in the XiveRouter for
simplicity.
When the IVRE has completed its job of matching an event source with a
Notification Virtual Target (NVT) to notify, it forwards the event
notification to the IVPE sub-engine. The IVPE scans the thread
interrupt contexts of the Notification Virtual Targets (NVT)
dispatched on the HW processor threads and if a match is found, it
signals the thread. If not, the IVPE escalates the notification to
some other targets and records the notification in a backlog queue.
The IVPE maintains the thread interrupt context state for each of its
NVTs not dispatched on HW processor threads in the Notification
Virtual Target table (NVTT).
The model currently only supports single NVT notifications.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
[dwg: Folded in fix for field accessors]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Each POWER9 processor chip has a XIVE presenter that can generate four
different exceptions to its threads:
- hypervisor exception,
- O/S exception
- Event-Based Branch (EBB)
- msgsnd (doorbell).
Each exception has a state independent from the others called a Thread
Interrupt Management context. This context is a set of registers which
lets the thread handle priority management and interrupt acknowledgment
among other things. The most important ones being :
- Interrupt Priority Register (PIPR)
- Interrupt Pending Buffer (IPB)
- Current Processor Priority (CPPR)
- Notification Source Register (NSR)
These registers are accessible through a specific MMIO region, called
the Thread Interrupt Management Area (TIMA), four aligned pages, each
exposing a different view of the registers. First page (page address
ending in 0b00) gives access to the entire context and is reserved for
the ring 0 view for the physical thread context. The second (page
address ending in 0b01) is for the hypervisor, ring 1 view. The third
(page address ending in 0b10) is for the operating system, ring 2
view. The fourth (page address ending in 0b11) is for user level, ring
3 view.
The thread interrupt context is modeled with a XiveTCTX object
containing the values of the different exception registers. The TIMA
region is mapped at the same address for each CPU.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
To complete the event routing, the IVRE sub-engine uses a second table
containing Event Notification Descriptor (END) structures.
An END specifies on which Event Queue (EQ) the event notification
data, defined in the associated EAS, should be posted when an
exception occurs. It also defines which Notification Virtual Target
(NVT) should be notified.
The Event Queue is a memory page provided by the O/S defining a
circular buffer, one per server and priority couple, containing Event
Queue entries. These are 4 bytes long, the first bit being a
'generation' bit and the 31 following bits the END Data field. They
are pulled by the O/S when the exception occurs.
The END Data field is a way to set an invariant logical event source
number for an IRQ. On sPAPR machines, it is set with the
H_INT_SET_SOURCE_CONFIG hcall when the EISN flag is used.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
[dwg: Fold in a later fix from Cédric fixing field accessors]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The XiveRouter models the second sub-engine of the XIVE architecture :
the Interrupt Virtualization Routing Engine (IVRE).
The IVRE handles event notifications of the IVSE and performs the
interrupt routing process. For this purpose, it uses a set of tables
stored in system memory, the first of which being the Event Assignment
Structure (EAS) table.
The EAT associates an interrupt source number with an Event Notification
Descriptor (END) which will be used in a second phase of the routing
process to identify a Notification Virtual Target.
The XiveRouter is an abstract class which needs to be inherited from
to define a storage for the EAT, and other upcoming tables.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
[dwg: Folded in parts of a later fix by Cédric fixing field access]
[dwg: Fix style nits]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
