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>
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