[SPARC64]: Fill dead cycles on trap entry with real work.

As we save trap state onto the stack, the store buffer fills up
mid-way through and we stall for several cycles as the store buffer
trickles out to the L2 cache.  Meanwhile we can do some privileged
register reads and other calculations, essentially for free.

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc64/kernel/etrap.S b/arch/sparc64/kernel/etrap.S
index 4a0e01b..f255614 100644 (file)
--- a/arch/sparc64/kernel/etrap.S
+++ b/arch/sparc64/kernel/etrap.S
@@ -98,37 +98,40 @@ etrap_save: save    %g2, -STACK_BIAS, %sp
                stxa    %g3, [%l4] ASI_DMMU
                sethi   %hi(KERNBASE), %l4
                flush   %l4
-               wr      %g0, ASI_AIUS, %asi
-2:             wrpr    %g0, 0x0, %tl
-               mov     %g4, %l4
+               mov     ASI_AIUS, %l7
+2:             mov     %g4, %l4
                mov     %g5, %l5
-
-               mov     %g7, %l2
+               add     %g7, 4, %l2
                wrpr    %g0, ETRAP_PSTATE1, %pstate
                stx     %g1, [%sp + PTREGS_OFF + PT_V9_G1]
                stx     %g2, [%sp + PTREGS_OFF + PT_V9_G2]
+               sllx    %l7, 24, %l7
                stx     %g3, [%sp + PTREGS_OFF + PT_V9_G3]
+               rdpr    %cwp, %l0
                stx     %g4, [%sp + PTREGS_OFF + PT_V9_G4]
                stx     %g5, [%sp + PTREGS_OFF + PT_V9_G5]
                stx     %g6, [%sp + PTREGS_OFF + PT_V9_G6]
-
                stx     %g7, [%sp + PTREGS_OFF + PT_V9_G7]
+               or      %l7, %l0, %l7
+               sethi   %hi(TSTATE_RMO | TSTATE_PEF), %l0
+               or      %l7, %l0, %l7
+               wrpr    %l2, %tnpc
+               wrpr    %l7, (TSTATE_PRIV | TSTATE_IE), %tstate
                stx     %i0, [%sp + PTREGS_OFF + PT_V9_I0]
                stx     %i1, [%sp + PTREGS_OFF + PT_V9_I1]
                stx     %i2, [%sp + PTREGS_OFF + PT_V9_I2]
                stx     %i3, [%sp + PTREGS_OFF + PT_V9_I3]
                stx     %i4, [%sp + PTREGS_OFF + PT_V9_I4]
                stx     %i5, [%sp + PTREGS_OFF + PT_V9_I5]
-
                stx     %i6, [%sp + PTREGS_OFF + PT_V9_I6]
-               stx     %i7, [%sp + PTREGS_OFF + PT_V9_I7]
-               wrpr    %g0, ETRAP_PSTATE2, %pstate
                mov     %l6, %g6
+               stx     %i7, [%sp + PTREGS_OFF + PT_V9_I7]
                LOAD_PER_CPU_BASE(%g5, %g6, %g4, %g3, %l1)
-               jmpl    %l2 + 0x4, %g0
-                ldx    [%g6 + TI_TASK], %g4
+               ldx     [%g6 + TI_TASK], %g4
+               done
 
-3:             ldub    [%l6 + TI_FPDEPTH], %l5
+3:             mov     ASI_P, %l7
+               ldub    [%l6 + TI_FPDEPTH], %l5
                add     %l6, TI_FPSAVED + 1, %l4
                srl     %l5, 1, %l3
                add     %l5, 2, %l5