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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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52
README.adoc
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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

10
lkmc/m5ops.h
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@@ -14,11 +14,11 @@
* D means RDI which is the first argument of a Linux C function call,
* and S means RSI is the second one: these are also used by gem5 as arguments of the m5ops.
*/
#define LKMC_M5OPS_CHECKPOINT_ASM mov $0, %%rdi; mov $0, %%rsi; .word 0x040F; .word 0x0043
#define LKMC_M5OPS_DUMPSTATS_ASM mov $0, %%rdi; mov $0, %%rsi; .word 0x040F; .word 0x0041
#define LKMC_M5OPS_EXIT_ASM mov $0, %%rdi; .word 0x040F; .word 0x0021
#define LKMC_M5OPS_FAIL_1_ASM mov $0, %%rdi; mov $1, %%rsi; .word 0x040F; .word 0x0022
#define LKMC_M5OPS_RESETSTATS_ASM mov $0, %%rdi; mov $0, %%rsi; .word 0x040F; .word 0x0040
#define LKMC_M5OPS_CHECKPOINT_ASM mov $0, %rdi; mov $0, %rsi; .word 0x040F; .word 0x0043
#define LKMC_M5OPS_DUMPSTATS_ASM mov $0, %rdi; mov $0, %rsi; .word 0x040F; .word 0x0041
#define LKMC_M5OPS_EXIT_ASM mov $0, %rdi; .word 0x040F; .word 0x0021
#define LKMC_M5OPS_FAIL_1_ASM mov $0, %rdi; mov $1, %rsi; .word 0x040F; .word 0x0022
#define LKMC_M5OPS_RESETSTATS_ASM mov $0, %rdi; mov $0, %rsi; .word 0x040F; .word 0x0040
#define LKMC_M5OPS_CHECKPOINT __asm__ __volatile__ (".word 0x040F; .word 0x0043;" : : "D" (0), "S" (0) :)
#define LKMC_M5OPS_DUMPSTATS __asm__ __volatile__ (".word 0x040F; .word 0x0041;" : : "D" (0), "S" (0) :)

8
path_properties.py
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@@ -543,7 +543,6 @@ path_properties_tuples = (
'linux': (
{},
{
'gem5_exit.S': {'allowed_emulators': {'gem5'}},
'wfe.S': {'more_than_1s': True},
'wfe_wfe.S': {'more_than_1s': True},
}
@@ -678,6 +677,13 @@ path_properties_tuples = (
'thread_return_value.cpp': {'test_run_args': {'cpus': 2}},
},
),
'freestanding': (
freestanding_properties,
{
'gem5_checkpoint_restore.S': {'allowed_emulators': {'gem5'}},
'gem5_exit.S': {'allowed_emulators': {'gem5'}},
}
),
'gcc': (
{**gnu_extension_properties, **{'cc_pedantic': False}},
{

12
run
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@@ -497,6 +497,12 @@ Extra options to append at the end of the emulator command line.
] +
gem5_exe_args
)
if self.env['gem5_restore'] is not None:
# https://cirosantilli.com/linux-kernel-module-cheat#gem5-checkpoint-internals
cpt_dirs = self.gem5_list_checkpoint_dirs()
cpt_dir = cpt_dirs[-self.env['gem5_restore']]
cpt_dirs_sorted_by_tick = sorted(cpt_dirs, key=lambda x: int(x.split('.')[1]))
extra_emulator_args.extend(['-r', str(cpt_dirs_sorted_by_tick.index(cpt_dir) + 1)])
if self.env['userland'] is not None:
cmd.extend([
self.env['gem5_se_file'], LF,
@@ -524,12 +530,6 @@ Extra options to append at the end of the emulator command line.
cmd.extend(['--interp-dir', self.env['userland_library_dir'], LF])
else:
if self.env['gem5_script'] == 'fs':
if self.env['gem5_restore'] is not None:
# https://cirosantilli.com/linux-kernel-module-cheat#gem5-checkpoint-internals
cpt_dirs = self.gem5_list_checkpoint_dirs()
cpt_dir = cpt_dirs[-self.env['gem5_restore']]
cpt_dirs_sorted_by_tick = sorted(cpt_dirs, key=lambda x: int(x.split('.')[1]))
extra_emulator_args.extend(['-r', str(cpt_dirs_sorted_by_tick.index(cpt_dir) + 1)])
cmd.extend([
self.env['gem5_fs_file'], LF,
'--kernel', self.env['image'], LF,

11
userland/freestanding/gem5_checkpoint_restore.S Normal file
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@@ -0,0 +1,11 @@
/* https://cirosantilli.com/linux-kernel-module-cheat#gem5-checkpoint-userland-minimal-example */
#define LKMC_M5OPS_ENABLE 1
#include "lkmc/m5ops.h"
.text
.global _start
_start:
asm_main_after_prologue:
LKMC_M5OPS_CHECKPOINT_ASM
LKMC_M5OPS_EXIT_ASM

10
userland/freestanding/gem5_exit.S Normal file
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@@ -0,0 +1,10 @@
/* https://cirosantilli.com/linux-kernel-module-cheat#benchmark-emulators-on-userland-executables */
#define LKMC_M5OPS_ENABLE 1
#include "lkmc/m5ops.h"
.text
.global _start
_start:
asm_main_after_prologue:
LKMC_M5OPS_EXIT_ASM