On 5/13/2025 1:37 PM, Sohil Mehta wrote:

The NMI-source bitmap is delivered as FRED event data to the kernel.
When available, use NMI-source based filtering to determine the exact
handlers to run.

Activate NMI-source based filtering only for Local NMIs. While handling
platform NMI types (such as SERR and IOCHK), do not use the source
bitmap. They have only one handler registered per type, so there is no
need to disambiguate between multiple handlers.

Some third-party chipsets may send NMI messages with a hardcoded vector
of 2, which would result in bit 2 being set in the NMI-source bitmap.
Skip the local NMI handlers in this situation.

Bit 0 of the source bitmap is set by the hardware whenever a source
vector was not used while generating an NMI, or the originator could not
be reliably identified. Poll all the registered handlers in that case.

When multiple handlers need to be executed, adhere to the existing
priority scheme and execute the handlers registered with NMI_FLAG_FIRST
before others.

The logic for handling legacy NMIs is unaffected since the source bitmap
would always have all bits set.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sohil Mehta <redacted>

Reviewed-by: Xin Li (Intel) <xin@zytor.com>