- The document discusses the MIPS R8000 CPU architecture used in SGI workstations and discusses issues with panic errors related to TLB and PTE entries on OpenBSD for the SGI IP26 platform. - It provides code snippets from OpenBSD showing functions and assembly related to the MIPS64 TLB, cache, and exception handling implementations for the R8000. - The discussion focuses on troubleshooting a "utlbmod" panic error seen at boot by examining the TLB and PTE implementations in OpenBSD for the R8000 CPU.

1. ?
OSC 2016 Nagoya
*BSD
@nullnilaki

2. sgi Indigo2

3. MIPS R8000
>> hinv
System: IP26
Processor: 75 Mhz R8000, with FPU
Primary I-cache size: 16 Kbytes
Primary D-cache size: 16 Kbytes
Secondary cache size: 2 Mbytes
Memory size: 512 Mbytes
Graphics: GR5-XZ
SCSI Disk: scsi(0)disk(1)
Audio: Iris Audio Processor: version A2 revision 1.1.0

4. MIPS R8000
M88k !
http://forums.nekochan.net/viewtopic.php?t=16726745

5. MIPS R8000
TLB 384 …

6. MIPS R8000
/*
* Initialize the kernel page table pointer.
* This is a no-op on non-R8000 processors.
*/
LEAF(tlb_set_gbase, 0)
j ra
nop
END(tlb_set_gbase)
/*
* void tlb_set_gbase(vaddr_t, vsize_t);
*/
LEAF(tlb_set_gbase, 0) /* { */
DMTC0 a0, COP_0_GBASE
MTC0_HAZARD
DMTC0 a1, COP_0_WORK1
MTC0_HAZARD
j ra
NOP
END(tlb_set_gbase) /* } */
…

7. MIPS R8000
…

8. MIPS R8000
R8000
SGI
Linux/MIPS
R8000
TLB
MIPS
R10000
Silicon Graphics
http://archive.linux.or.jp/JF/JFdocs/MIPS-HOWTO-9.html#ss9.8

9. R8000( )…

10. R8000( )…

11. R8000( )…

12. R8000( ) ( ´)

13. http://d.hatena.ne.jp/syuu1228/20090805
…

14. RAM disk kernel ?
RAM disk kernel ?
OpenBSD sgimips (Fuel )

15. ?
Set name(s)? (or 'abort' or 'done') [done]
Cannot determine prefetch area. Continue without verification? [no] yes
Installing base57.tgz 100% |**************************| 56003 KB 03:49
Extracting etc.tgz 100% |**************************| 110 KB 00:00
Location of sets? (disk http nfs or 'done') [http] done
Are you *SURE* your install is complete without 'bsd.IP26'? [no] yes
Time appears wrong. Set to 'Sun Sep 6 08:56:36 JST 2015'? [yes]
Saving configuration files...done.
Making all device nodes...sh(8003) in realloc(): error: chunk info corrupted
Abort trap
done.
Installing boot loader in volume header.
Writing file /mnt/usr/mdec/boot-IP26
sgivol: stat /mnt/usr/mdec/boot-IP26: No such file or directory
WARNING: Boot install failed. Booting from disk will not be possible
IP26 RAM disk kernel RAM disk kernel netboot
(ftp.jaist.ac.jp ) base57.tgz
OpenBSD IP26
base57.tgz ” ”

16. ?
/src/distrib/sgi/ramdisk/install.md
md_installboot() {
local _disk=$1
echo "Installing boot loader in volume header."
if ! /usr/mdec/sgivol -w boot /mnt/usr/mdec/boot-$IPARCH $_disk; then
echo "nWARNING: Boot install failed. Booting from disk will not be possible"
fi
for _k in /mnt/bsd{,.mp,.rd}; do
[[ -f $_k.$IPARCH ]] && mv $_k.$IPARCH $_k
done
}

17. Makefile boot-IP26

18. RAM disk kernel ftp
NetBSD sysinst(install kernel) ?ftp
OpenBSD ftp
anonymous ftp

19. # /mnt/usr/mdec/sgivol -w boot /mnt/usr/mdec/boot-IP26 sd0
Writing file /mnt/usr/mdec/boot-IP26
File /mnt/usr/mdec/boot-IP26 has 101640 bytes
disklabel shows 17783112 sectors with 512 bytes per sector
checksum: 00000000
root part: 0
swap part: 1
bootfile: /bsd
Volume header files:
boot offset 2 blocks, length 101640 bytes (199 blocks)
SGI partitions:
0:a blocks 17779977 first 3135 type 4 (BSD4.2)
8:i blocks 3135 first 0 type 0 (Volume Header)
10:k blocks 17783112 first 0 type 6 (Volume)
# mv /mnt/usr/mdec/bsd.IP26 /mnt/bsd
ftp …
!

20. NFS
•
OS
NFS !
( NIC )
•
NFS
NFS
!

21. ?

22. ?
OS panic R8000
R8000
OpenBSD R8000

23. utlbmod?
>> bootp()bsd.rd.IP26
Obtaining bsd.rd.IP26 from server macbook2006
3577592+722344 entry: 0xa800000008010000
ARCS64 Firmware
Found SGI-IP26, setting up.
...
panic: trap: utlbmod: invalid pte
Stopped at 0xa800000008294424: jr ra
0xa800000008294428: move zero,zero
utlbmod panic !

24. TLB ?

25. TLB ?
• OS panic utlbmod
• OS panic …
PTE ?
• ….
?
• C
…

26. TLB ?
…

27. C
/sys/arch/mips64/include/pmap.h
/* User virtual address to pte page entry */
#define uvtopte(va) (((va) >> PAGE_SHIFT) & (NPTEPG -1))
”2”

28. Multi-user

30. !
OpenBSD
…

31. …

32. sgi CPU !

33. diff

34. ?
• MIPS R8000 CPU …
• MIPS R8000 …
/src/sys/arch/mips64/mips64/cache_tfp.c
/src/sys/arch/mips64/mips64/cache_tfp_subr.S
/src/sys/arch/mips64/mips64/exception_tfp.S
/src/sys/arch/mips64/mips64/tlb_tfp.S
• miod

35. …
SIGBUS SIGSEGV

36. …
The 2 in the original code is log2(pte size); k0 >> PAGE_SHIFT will be
the pte number. But in the page table, it is stored as an array of
32-bit words, so we need to shift it to the left by 2. The original
instructions:
PTR_SRL k0, PAGE_SHIFT - 2
andi k0, ((NPTEPG / 2) - 1) << 2
are equivalent to:
PTR_SRL k0, PAGE_SHIFT
andi k0, (NPTEPG / 2) - 1
PTR_SLL k0, 2
and guarantees the address is correctly aligned for the `lwu'
instruction later.

37. 2 !
0 0
1 4
2 8
3 12
…
Page table
index Page tabe
Page fault
Page table index
PTE_LOG
index
PTR_SRL k0, PAGE_SHIFT - PTE_LOG
andi k0, (NPTEPG - 1) << PTE_LOG
Page table
PTR_ADDU k1, k0
PTE_LOAD k0, 0(k1) # get pte
#define PTE_LOG 2
@n_soda
!

38. mips RISC -R2000/ R3000-
ISBN-10: 4320025989
NIX
ISBN-10: 4320025989
MIPS( )
R8000 User Manual
….
http://nullnilaki.hatenablog.com/entries/2015/12/23
Miod @MiodVallat
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