linux/arch/sparc/kernel/urtt_fill.S
Babu Moger 0ae2d26ffe arch/sparc: Avoid DCTI Couples
Avoid un-intended DCTI Couples. Use of DCTI couples is deprecated.
Also address the "Programming Note" for optimal performance.

Here is the complete text from Oracle SPARC Architecture Specs.

6.3.4.7 DCTI Couples
"A delayed control transfer instruction (DCTI) in the delay slot of
another DCTI is referred to as a “DCTI couple”. The use of DCTI couples
is deprecated in the Oracle SPARC Architecture; no new software should
place a DCTI in the delay slot of another DCTI, because on future Oracle
SPARC Architecture implementations DCTI couples may execute either
slowly or differently than the programmer assumes it will.

SPARC V8 and SPARC V9 Compatibility Note
The SPARC V8 architecture left behavior undefined for a DCTI couple. The
SPARC V9 architecture defined behavior in that case, but as of
UltraSPARC Architecture 2005, use of DCTI couples was deprecated.
Software should not expect high performance from DCTI couples, and
performance of DCTI couples should be expected to decline further in
future processors.

Programming Note
As noted in TABLE 6-5 on page 115, an annulled branch-always
(branch-always with a = 1) instruction is not architecturally a DCTI.
However, since not all implementations make that distinction, for
optimal performance, a DCTI should not be placed in the instruction word
immediately following an annulled branch-always instruction (BA,A or
BPA,A)."

Signed-off-by: Babu Moger <babu.moger@oracle.com>
Reviewed-by: Rob Gardner <rob.gardner@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-03-27 21:51:40 -07:00

100 lines
1.8 KiB
ArmAsm

#include <asm/thread_info.h>
#include <asm/trap_block.h>
#include <asm/spitfire.h>
#include <asm/ptrace.h>
#include <asm/head.h>
.text
.align 8
.globl user_rtt_fill_fixup_common
user_rtt_fill_fixup_common:
rdpr %cwp, %g1
add %g1, 1, %g1
wrpr %g1, 0x0, %cwp
rdpr %wstate, %g2
sll %g2, 3, %g2
wrpr %g2, 0x0, %wstate
/* We know %canrestore and %otherwin are both zero. */
sethi %hi(sparc64_kern_pri_context), %g2
ldx [%g2 + %lo(sparc64_kern_pri_context)], %g2
mov PRIMARY_CONTEXT, %g1
661: stxa %g2, [%g1] ASI_DMMU
.section .sun4v_1insn_patch, "ax"
.word 661b
stxa %g2, [%g1] ASI_MMU
.previous
sethi %hi(KERNBASE), %g1
flush %g1
mov %g4, %l4
mov %g5, %l5
brnz,pn %g3, 1f
mov %g3, %l3
or %g4, FAULT_CODE_WINFIXUP, %g4
stb %g4, [%g6 + TI_FAULT_CODE]
stx %g5, [%g6 + TI_FAULT_ADDR]
1:
mov %g6, %l1
wrpr %g0, 0x0, %tl
661: nop
.section .sun4v_1insn_patch, "ax"
.word 661b
SET_GL(0)
.previous
wrpr %g0, RTRAP_PSTATE, %pstate
mov %l1, %g6
ldx [%g6 + TI_TASK], %g4
LOAD_PER_CPU_BASE(%g5, %g6, %g1, %g2, %g3)
brnz,pn %l3, 1f
nop
call do_sparc64_fault
add %sp, PTREGS_OFF, %o0
ba,pt %xcc, rtrap
nop
1: cmp %g3, 2
bne,pn %xcc, 2f
nop
sethi %hi(tlb_type), %g1
lduw [%g1 + %lo(tlb_type)], %g1
cmp %g1, 3
bne,pt %icc, 1f
add %sp, PTREGS_OFF, %o0
mov %l4, %o2
call sun4v_do_mna
mov %l5, %o1
ba,a,pt %xcc, rtrap
1: mov %l4, %o1
mov %l5, %o2
call mem_address_unaligned
nop
ba,a,pt %xcc, rtrap
2: sethi %hi(tlb_type), %g1
mov %l4, %o1
lduw [%g1 + %lo(tlb_type)], %g1
mov %l5, %o2
cmp %g1, 3
bne,pt %icc, 1f
add %sp, PTREGS_OFF, %o0
call sun4v_data_access_exception
nop
ba,a,pt %xcc, rtrap
nop
1: call spitfire_data_access_exception
nop
ba,a,pt %xcc, rtrap