docs(x86_64): add explantory comment to qemu_exit

[mkroening]

Cherry-picked from #1995.

[mkroening]

CC: @hcsch

[github-actions]

Benchmark Results

Benchmark	Current: 95da0e0	Previous: 6019ba4	Performance Ratio
startup_benchmark Build Time	110.80 s	110.61 s	1.00
startup_benchmark File Size	0.89 MB	0.91 MB	0.99
Startup Time - 1 core	0.90 s (±0.04 s)	0.93 s (±0.03 s)	0.97
Startup Time - 2 cores	0.91 s (±0.03 s)	0.93 s (±0.04 s)	0.97
Startup Time - 4 cores	0.92 s (±0.03 s)	0.94 s (±0.03 s)	0.98
multithreaded_benchmark Build Time	111.12 s	110.93 s	1.00
multithreaded_benchmark File Size	1.00 MB	1.01 MB	0.99
Multithreaded Pi Efficiency - 2 Threads	87.81 % (±8.53 %)	92.34 % (±7.09 %)	0.95
Multithreaded Pi Efficiency - 4 Threads	44.10 % (±3.58 %)	44.95 % (±3.07 %)	0.98
Multithreaded Pi Efficiency - 8 Threads	25.80 % (±2.20 %)	25.64 % (±1.60 %)	1.01
micro_benchmarks Build Time	272.97 s	273.99 s	1.00
micro_benchmarks File Size	1.01 MB	1.01 MB	0.99
Scheduling time - 1 thread	155.38 ticks (±22.49 ticks)	162.90 ticks (±21.02 ticks)	0.95
Scheduling time - 2 threads	89.21 ticks (±15.88 ticks)	89.13 ticks (±11.93 ticks)	1.00
Micro - Time for syscall (getpid)	10.78 ticks (±5.70 ticks)	10.81 ticks (±4.73 ticks)	1.00
Memcpy speed - (built_in) block size 4096	57124.91 MByte/s (±42402.96 MByte/s)	64709.21 MByte/s (±45699.60 MByte/s)	0.88
Memcpy speed - (built_in) block size 1048576	16334.83 MByte/s (±13509.23 MByte/s)	15408.89 MByte/s (±12426.51 MByte/s)	1.06
Memcpy speed - (built_in) block size 16777216	11605.15 MByte/s (±9458.80 MByte/s)	11558.07 MByte/s (±9407.44 MByte/s)	1.00
Memset speed - (built_in) block size 4096	57020.65 MByte/s (±42332.99 MByte/s)	64775.93 MByte/s (±45733.35 MByte/s)	0.88
Memset speed - (built_in) block size 1048576	16498.65 MByte/s (±13575.99 MByte/s)	15762.33 MByte/s (±12632.18 MByte/s)	1.05
Memset speed - (built_in) block size 16777216	12349.38 MByte/s (±10313.51 MByte/s)	11893.62 MByte/s (±9629.31 MByte/s)	1.04
Memcpy speed - (rust) block size 4096	55515.30 MByte/s (±40776.20 MByte/s)	54010.26 MByte/s (±39296.64 MByte/s)	1.03
Memcpy speed - (rust) block size 1048576	16133.24 MByte/s (±12859.20 MByte/s)	15677.56 MByte/s (±12448.09 MByte/s)	1.03
Memcpy speed - (rust) block size 16777216	11460.56 MByte/s (±9326.48 MByte/s)	11260.20 MByte/s (±9144.57 MByte/s)	1.02
Memset speed - (rust) block size 4096	54470.61 MByte/s (±40485.91 MByte/s)	54756.81 MByte/s (±39887.77 MByte/s)	0.99
Memset speed - (rust) block size 1048576	16034.25 MByte/s (±12809.30 MByte/s)	16095.43 MByte/s (±12723.66 MByte/s)	1.00
Memset speed - (rust) block size 16777216	11548.12 MByte/s (±9356.10 MByte/s)	11569.34 MByte/s (±9343.13 MByte/s)	1.00
alloc_benchmarks Build Time	261.80 s	266.80 s	0.98
alloc_benchmarks File Size	0.96 MB	0.97 MB	0.99
Allocations - Allocation success	100.00 %	100.00 %	1
Allocations - Deallocation success	100.00 %	100.00 %	1
Allocations - Pre-fail Allocations	100.00 %	100.00 %	1
Allocations - Average Allocation time	15906.29 Ticks (±659.67 Ticks)	11934.55 Ticks (±589.33 Ticks)	1.33
Allocations - Average Allocation time (no fail)	15906.29 Ticks (±659.67 Ticks)	11934.55 Ticks (±589.33 Ticks)	1.33
Allocations - Average Deallocation time	2027.28 Ticks (±494.61 Ticks)	2238.08 Ticks (±305.33 Ticks)	0.91
mutex_benchmark Build Time	265.95 s	265.84 s	1.00
mutex_benchmark File Size	1.01 MB	1.02 MB	0.99
Mutex Stress Test Average Time per Iteration - 1 Threads	31.98 ns (±2.35 ns)	33.24 ns (±2.55 ns)	0.96
Mutex Stress Test Average Time per Iteration - 2 Threads	27.18 ns (±3.43 ns)	27.66 ns (±3.09 ns)	0.98

This comment was automatically generated by workflow using github-action-benchmark.