some systems were designed so that AML writes to various resources shared
with OS drivers, including the RTC, PIC, PCI, etc. These writes could
collide with writes by the OS and should never be performed. For now, we
print a message if such an access occurs, but do not block it. To block
the access, the tunable "debug.acpi.block_bad_io" can be set to 1. In the
future, we will flip the switch and this will become the default.
Information about this problem was found in Microsoft KB 283649. They
block IO accesses if the BIOS indicates via _OSI that it is Windows 2001
or higher. They always block accesses to the PIC, cascaded PIC, and ELCRs,
no matter how old the BIOS.
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