
Sun Microelectronics
238
UltraSPARC User’s Manual
and FFFF F7FF FFFF FFFF
16
inclusive are termed “out-of-range” and are illegal.
Address translation and MMU related descriptions can be found in Section 4.2,
“Virtual Address Translation,” on page 21.
Figure 14-2
UltraSPARC’s 44-bit Virtual Address Space, with Hole (Same as Figure 4-2)
Note:
Throughout this document, when virtual address fields are specified as
64-bit quantities, they are assumed to be sign-extended based on VA<43>.
A number of state registers are affected by the reduced virtual address space.
TBA, TPC, TNPC, VA and PA watchpoint, and DMMU SFAR registers are 44-bits,
sign-extended to 64-bits on read accesses. No checks are done when these regis-
ters are written by software. It is the responsibility of privileged software to prop-
erly update these registers.
An out of range address during an instruction access causes an
instruction_access_exception
trap if PSTATE.AM is not set.
If the target address of a JMPL or RETURN instruction is an out-of-range address
and PSTATE.AM is not set, a trap is generated with the PC = the address of the
JMPL or RETURN instruction and the trap type in the I-MMU SFSR register. This
instruction_access_exception
trap is lower priority than other traps on the JMPL or
RETURN (
illegal_instruction
due to nonzero reserved fields in the JMPL or RE-
TURN,
mem_address_not_aligned
trap, or
window_fill
trap), because it really applies
to the target. The trap handler can determine the out-of-range address by decod-
ing the JMPL instruction from the code.
All other control transfer instructions trap on the PC of the target instruction
along with different status in the I-MMU SFSR register. Because the PC is sign-ex-
tended to 64 bits, the trap handler must adjust the PC value to compute the fault-
FFFF FFFF FFFF FFFF
FFFF F800 0000 0000
0000 0000 0000 0000
0000 07FF FFFF FFFF
Out of Range VA
(VA “Hole”)
FFFF F7FF FFFF FFFF
0000 0800 0000 0000
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