TLB-miss counter in TLB-miss handler (important proposal).

["Naruaki.Etomi" <nullnilaki%gmail.com@localhost>]

This is important proposal.

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Prerequisite:
%hi %lo operator that takes an address as an argument does not work on
mips64 kernel.

Like below:
lui k1, %hi(CPUVAR(CURLWP)) #05: k1=hi of curlwp
jr k0 #06
PTR_L k1, %lo(CPUVAR(CURLWP))(k1) #07: k1=lo of curlwp

Because:
LUI instruction means:
The immediate value is shifted left "16 bits" and stored in the
register. The lower 16 bits are zeroes.

Adress 0x0011aabbccddeeff (64 bit) is processed as follows:

lui k1, 0x0011aabbccddeeff
-> k1 = 0xffffffffccde0000

PTR_L k1, %lo(0x0011aabbccddeeff)(k1)
-> ld k1, 0xffffffffeeff0000(0xffffffffccde0000)
-> Load from chaos!

However, The higher 32bits are f adress(0xffffffffaabbccd like O2 etc) is work.
makeoptions TEXTADDR="0xffffffff80069000" # entry point
https://nxr.netbsd.org/xref/src/sys/arch/sgimips/conf/GENERIC64_IP3x#29

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I rewrite %hi %lo operator code.
https://github.com/nullnilaki/NetBSD-mips64/commit/2729f32536de2fedefdd5d828f6fa918d991e555

And I discovered below.
https://nxr.netbsd.org/xref/src/sys/arch/mips/mips/mipsX_subr.S#498

#if (MIPS3 + MIPS64 + MIPS64R2) > 0
lui k1, %hi(CPUVAR(EV_TLBMISSES)) #1b: k1=hi of tlbmisses
REG_L k0, %lo(CPUVAR(EV_TLBMISSES))(k1) #1c
REG_ADDU k0, 1 #1d
REG_S k0, %lo(CPUVAR(EV_TLBMISSES))(k1) #1e
#endif

I rewrite this code.
Like below:

+#if (MIPS3 + MIPS64 + MIPS64R2) > 0
+       dla     k1, (CPUVAR(EV_TLBMISSES))
+       ld      k0, 0(k1) #1c
+       REG_ADDU k0, 1                          #1d
+       sd      k0, 0(k1) #1e
+#endif

Howerver, There are many instructions...

--- mips3_subr.o ---
/usr/src/sys/arch/mips/mips/mipsX_subr.S: Assembler messages:
/usr/src/sys/arch/mips/mips/mipsX_subr.S:509: Error: attempt to move
.org backwards
/usr/src/sys/arch/mips/mips/mipsX_subr.S:660: Error: attempt to move
.org backwards
*** [mips3_subr.o] Error code 1

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I think TLB-miss handler should be especially simple.

I want to delete TLB-miss counter code.
Like below:
https://github.com/nullnilaki/NetBSD-mips64/commit/c13ff030cffbd90f69e2fe438204a7f630f2ffb9

Please confirm that I may take this course of action.

-- 
Naruaki Etomi
nullnilaki%gmail.com@localhost