Specifications

172
Type Name Description
Instruction Access Rights
Instruction Access-Bit
Instruction Key Miss
Instruction TLB
Key Permission
Lower-Privilege Transfer
Trap
NaT Consumption
Page Not Present
Single Step Trap Used
Speculation
Taken Branch Trap
Unaligned Reference
Unsupported Data Reference
VHPT Translation
Mixed EFI and Traditional Environment
The mixed EFI and traditional environment imposes several complexities over the EFI-
only environment. The main complexity is a transition to/from 32-bit/16-bit mode. An
additional complexity is that the traditional environment must handle many more
interrupts as devices are interrupt driven versus polled. The hardware and software
interrupts that are used depend upon the traditional OpROMs invoked. The following is a
high-level view and the reader should refer to the appropriate AMI* or Phoenix* BIOS
specifications for details.
1. Set the appropriate flags as current operating mode.
2. Allocate area on the 16-bit stack for registers.
3. Copy current EFI registers to 16-bit stack.
4. Save the current interrupt state.
5. Disable interrupts.
6. Change the interrupt mask to traditional mode.
7. Invoke EFI to legacy thunk code.
8. Perform legacy operations.
9. Disable interrupts; traditional code may re-enable them.
10. Change the interrupt mask to EFI mode.
11. Thunk back to EFI.
12. Restore the interrupt state.