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mike_hearn | on: Exploiting System Management Mode with a very long interrupt
The designers of the firmware anticipate this attack but punt it to the vendor, apparently:

    //
    // Platform implementor should choose a timeout value appropriately:
    
    [snip]

    // - The timeout value must be longer than longest possible IO operation in the system
wtallis | parent
I wonder whether a Thunderbolt accessory can cause arbitrarily long IO operations. What's the upper bound before some other layer gives up and causes the instruction to fault?
M95D | root | parent
No need. Thunderbolt is usually susceptible to DMA attacks.