ATM Switch WUGS

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ATM Switch WUGS

• Darron Yi Zhang

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Topics of Discussion

• Overview of WUGS
• SPC Hardware
• SPC Software
• SPC Utility

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Motivation

• Active Networking
• Network Probe
• High performance router
• PC as router is VERY limited
• (Gigabit/s Processing) on each port

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WUGS-20 Packaging
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Overview of WUGS
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Overview of WUGS(continued)
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• Smart Port Card
• Hardware

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The Smart Port Card

• Hardware
• SPC as a PC
• How do they each boot?
• SPC Hardware Components
• What roles do they play?

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Typical Pentium PC
CPU/Memory Bus
Addr/Data
Ctrl
Ctrl
CPU
North- Bridge
Cache
DRAM
Addr/Data/Ctrl
PCI Bus
Intr
NMI
INIT
SouthBridge (PIIX3) (PIC, PIT, )
PCI Devices
ISA Bus
ISA Devices
BIOS
Super-IO
BIOS
RTC Uarts Kbd/Mse Floppy Parallel ...
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How NetBSD Boots on a PC

• Components
• Pentium
• Boot ROM (replaced by BIOS in modern systems)
• BIOS
• Bootloader
• Kernel

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What SPC Needs
CPU/Memory Bus
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SPC Architecture
Addr/Data
Ctrl
Ctrl
CPU
North- Bridge
Cache
DRAM
Addr/Data/Ctrl
PCI Bus
NMI
INIT
Intr
APIC
PIT
PIC
RTC
UART1 Interface
BIOS ROM
Link Interface
UART2 Interface
Switch Interface
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SPC Photo
Switch Interface
DRAM
Link Interface
CPU Module
APIC
PCI Bus
System FPGA
Serial Ports
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SPC Components

• APIC
• PCI Bus Master
• Pentium Embedded Module
• 166 MHz MMX Pentium Processor
• L1 Cache 16KB Data, 16KB Code
• L2 cache 512 KB
• NorthBridge - 33 MHz, 32 bit PCI Bus
• PCI Bus Master
• System FPGA
• PCI Bus Slave
• Xilinx XC4020XLA-1 FPGA
• 20K Equivalent Gates
• 75 used

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SPC Components (continued)

• Memory
• EDO DRAM
• 64MB (Max for current design)
• Switch Interface - 1 Gb Utopia
• Link Interface - 1 Gb Utopia
• UART
• Two Serial Ports
• NetBSD system console
• TTY port

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System FPGA

• Coded in VHDL
• PCI slave device
• Replaces some of the PIIX3 (south bridge)
• Replaces some of the BIOS
• Replaces some of the Super IO Chip
• Provides reset capability

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System FPGA PIIX3 Functionality

• Programmable Interrupt Controller (PIC)
• Four Interrupts supported and statically
  assigned
• PIT (IRQ 0)
• APIC (IRQ 5)
• COM1 (IRQ 4)
• COM2 (IRQ 3)
• Static fully-nested interrupt priority structure.
• Specific End of Interrupt is the only EOI mode
  supported
• Programmable Interval Timer (PIT)
• generates a clock interrupt for NetBSD every
  10ms
• Reset - covered in a later slide

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System FPGA BIOS Functionality

• Interrupt functionality replaced by static values
• Simple 16 word by 32-bit ROM
• implements loop waiting for location 0xFFE00 to
  change value
• then jumps to boot loader code

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System FPGA Super IO Chip Functionality

• UART Interface
• Two Serial lines supported
• Fixed IRQs
• Real Time Clock
• only the register accesses of the RTC are
  supported
• no interrupts supported

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System FPGA Reset

• SPC needs a reset before every download
• switch reset
• causes SPC to be reset
• causes all connections in switch to be lost
• System FPGA reset
• causes SPC to be reset
• has no effect on the switch
• Normal SouthBridge reset
• I/O Register 0xCF9
• Hard Reset assert CPURST, PCIRST, and RSTDRV
• write 0xCF9 0x02 (00000010b)
• write 0xCF9 0x06 (00000110b)
• Soft Reset assert INIT
• write 0xCF9 0x00 (00000000b)
• write 0xCF9 0x04 (00000100b)

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System FPGA Reset

• SPC Reset
• a sequence of two writes to memory addresses
• APIC Control cells can write to
• memory addresses
• configuration registers
• NOT I/O Registers! Argh...
• To mimic the reset structure of the SB we use
• 0xFFFFFFF0
• 0xFFFFFFF4
• Hard Reset (all we really care about)
• write 0xFFFFFFF0 0x02 (00000010b)
• write 0xFFFFFFF4 0x06 (00000110b)

bits
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• Smart Port Card
• Software

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Software Overview

• SPC Specific Kernel Modifications
• Building a Kernel
• config
• compile
• Loading Kernel onto SPC to execute it
• download via APIC
• Initiating Kernel execution
• boot loader
• Configuring Devices
• APIC

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The Download Process
0x0
Bootloader
RESET
0x03FC
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
Download Program
0x0FFE00
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
0x0100000
Kernel
0xFFFFFFF0
Boot ROM
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• SPC Utilities

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Utilities - Overview

• Purpose of SPC Utilities
• glue between various software components
• simplify other parts of the system
• solve miscellaneous problems encountered
• Utilities that are still useful
• mkimg - make image
• mknl - make namelist

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mkimg - overview

• Creates a kernel image suitable for downloading
  to the SPC
• Removes some of the burden from the bootloader

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Kernel Image
On Disk

• This is what the NetBSD kernel in a.out format
  looks like on the disk
• e.g. the file /netbsd on most systems

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Kernel Image

• This is what the kernel image looks like when
  loaded into memory.
• Whats different?
• BSS segment has been inserted in the middle.

In Memory (as loaded by bootloader)
On Disk (e.g. the file /netbsd)
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mkimg - summary

• Kernel requires BSS segment for execution.
• Normal PC done at boot time (by the bootloader)
• SPC done by mkimg, after kernel build
• mkimg creates a copy of the kernel file with the
  BSS segment included.
• mkimg is invoked by make from the mk.3 script

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mknl - purpose

• Certain system tools need a kernel namelist
• ps, netstat, top, uptime, etc.
• Normally, this is read from kernel file (/netbsd)
• Problem kernel too large to fit on filesystem
• Solution
• create a file that we can put on the filesystem,
  to hold the namelist information
• file should look as much like the real kernel as
  possible

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Kernel Image
On Disk (e.g. the file /netbsd)

• mknl utility
• input kernel in a.out format
• output the symbols only file
• approach
• open input and output files
• copy exec header
• lseek past text and data segments
• copy symbol table and string table
• close files

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a file with a hole

• mknl creates a file with a hole
• unneeded blocks are not allocated
• Example of a file with a hole

block array for the file
disk block
disk block
null
null
null
null
disk block
disk block
. . .
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output from mknl
Output file from mknl
exec header
hole (used to be text segment)

• This is what the symbols-only netbsd file looks
  like
• This is what we put into our filesystem as
  /netbsd
• Doesnt require much space
• typically around 150kB
• Example from a 24MB kernel

hole (used to be initialized data)
symbol table
string table
152 -rw-r--r-- 1 root wheel 24624114 /netbsd
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mknl - implications

• Implication of a files with holes
• Copying can produce undesirable results holes
  look like blocks full of zeroes...
• new file will be as large as the original kernel
• defeats purpose of mknl
• Need to mknl directly into the filesystem.
• Need to mknl after any changes are made to the
  kernel.

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• Thank you!!!