On 4/16/24 22:47, Boris Ostrovsky wrote:
When a processor is running in SMM and receives INIT message the interrupt is left pending until SMM is exited. On the other hand, SIPI, which typically follows INIT, is discarded. This presents a problem since sender has no way of knowing that its SIPI has been dropped, which results in processor failing to come up. Keeping the SIPI pending avoids this scenario.
This is incorrect - it's yet another ugly legacy facet of x86, but we have to live with it. SIPI is discarded because the code is supposed to retry it if needed ("INIT-SIPI-SIPI").
The sender should set a flag as early as possible in the SIPI code so that it's clear that it was not received; and an extra SIPI is not a problem, it will be ignored anyway and will not cause trouble if there's a race.
What is the reproducer for this? Paolo
