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userland: freestanding gem5 checkpoint restore examples

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Ciro Santilli 六四事件 法轮功
2020-02-20 00:00:01 +00:00
parent 9015fd7042
commit 8447a9a8a7
6 changed files with 88 additions and 15 deletions
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@@ -11211,8 +11211,10 @@ Analogous to QEMU's <<snapshot>>, but better since it can be started from inside
Documentation: http://gem5.org/Checkpoints
To see it in action try:
....
./run --arch arm --emulator gem5
./run --arch aarch64 --emulator gem5
....
In the guest, wait for the boot to end and run:
@@ -11268,6 +11270,50 @@ Then there is no need to pass the kernel command line again to gem5 for replay:
since boot has already happened, and the parameters are already in the RAM of the snapshot.
==== gem5 checkpoint userland minimal example
In order to debug checkpoint restore bugs, this minimal setup using link:userland/freestanding/gem5_checkpoint_restore.S[] can be handy:
....
./build-userland --arch aarch64 --static
./run --arch aarch64 --emulator gem5 --static --userland userland/freestanding/gem5_checkpoint_restore.S --trace-insts-stdout
./run --arch aarch64 --emulator gem5 --static --userland userland/freestanding/gem5_checkpoint_restore.S --trace-insts-stdout --gem5-restore 1
./run --arch aarch64 --emulator gem5 --static --userland userland/freestanding/gem5_checkpoint_restore.S --trace-insts-stdout --gem5-restore 1 -- --cpu-type=DerivO3CPU --restore-with-cpu=DerivO3CPU --caches
....
On the initial run, we see that all instructions are executed and the checkpoint is taken:
....
0: system.cpu: A0 T0 : @asm_main_after_prologue : movz x0, #0, #0 : IntAlu : D=0x0000000000000000 flags=(IsInteger)
500: system.cpu: A0 T0 : @asm_main_after_prologue+4 : movz x1, #0, #0 : IntAlu : D=0x0000000000000000 flags=(IsInteger)
1000: system.cpu: A0 T0 : @asm_main_after_prologue+8 : m5checkpoint : IntAlu : flags=(IsInteger|IsNonSpeculative|IsUnverifiable)
Writing checkpoint
warn: Checkpoints for file descriptors currently do not work.
info: Entering event queue @ 1000. Starting simulation...
1500: system.cpu: A0 T0 : @asm_main_after_prologue+12 : movz x0, #0, #0 : IntAlu : D=0x0000000000000000 flags=(IsInteger)
2000: system.cpu: A0 T0 : @asm_main_after_prologue+16 : m5exit : No_OpClass : flags=(IsInteger|IsNonSpeculative)
Exiting @ tick 2000 because m5_exit instruction encountered
....
Then, on the first restore run, the checkpoint is restored, and only instructions after the checkpoint are executed:
....
info: Entering event queue @ 1000. Starting simulation...
1500: system.cpu: A0 T0 : @asm_main_after_prologue+12 : movz x0, #0, #0 : IntAlu : D=0x0000000000000000 flags=(IsInteger)
2000: system.cpu: A0 T0 : @asm_main_after_prologue+16 : m5exit : No_OpClass : flags=(IsInteger|IsNonSpeculative)
Exiting @ tick 2000 because m5_exit instruction encountered
....
and a similar thing happens for the restore with a different CPU type:
....
info: Entering event queue @ 1000. Starting simulation...
79000: system.cpu: A0 T0 : @asm_main_after_prologue+12 : movz x0, #0, #0 : IntAlu : D=0x0000000000000000 FetchSeq=1 CPSeq=1 flags=(IsInteger)
Exiting @ tick 84500 because m5_exit instruction encountered
....
Here we don't see the last `m5 exit` instruction on the log, but it must just be something to do with the O3 logging.
==== gem5 checkpoint internals
Checkpoints are stored inside the <<m5out-directory>> at:
@@ -19905,7 +19951,7 @@ Summary of manually collected results on <<p51>> at LKMC a18f28e263c91362519ef55
|gem5 optimized build immediate exit on first instruction to benchmark the simulator startup time
|ab6f7331406b22f8ab6e2df5f8b8e464fb35b611
|immediate exit link:userland/arch/aarch64/freestanding/linux/gem5_exit.S[] `-O0`
|immediate exit link:userland/freestanding/gem5_exit.S[] `-O0`
|`gem5 --arch aarch64`
|1
|1
@@ -19914,7 +19960,7 @@ Summary of manually collected results on <<p51>> at LKMC a18f28e263c91362519ef55
|same as above but debug build
|ab6f7331406b22f8ab6e2df5f8b8e464fb35b611
|link:userland/arch/aarch64/freestanding/linux/gem5_exit.S[] `-O0`
|link:userland/freestanding/gem5_exit.S[] `-O0`
|`gem5 --arch aarch64 --gem5-build-type debug`
|1
|1