A KVM Virtual Machine Manager in JavaScript
this is an attempt to build a functioning and useful virtual machine manager (vmm) completely in JavaScript, on the "lo" JavaScript runtime.
lo vmm.js- CPU: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
- OS: 22.04.1-Ubuntu
- Kernel: 6.5.0-35-generic
- guest vm allocated 30 MB RAM, times in nanoseconds, memory in bytes
KVM_CREATE_VM 15823979 15823979 rss 37683200
KVM_SET_TSS_ADDR 67443 15891422 rss 37683200
KVM_SET_IDENTITY_MAP_ADDR 54573 15945995 rss 37683200
mmap guest ram 56329 16002324 rss 37683200
KVM_SET_USER_MEMORY_REGION 92621 16094945 rss 37683200
KVM_CREATE_VCPU 525789 16620734 rss 37683200
init sreg 72161 16692895 rss 37683200
init reg 36530 16729425 rss 37683200
init cpuid 74564 16803989 rss 37683200
init msrs 30150 16834139 rss 37683200
read bzImage 411313 17245452 rss 37683200
load kernel image 1073504 18318956 rss 39387136
set bootparams 26134 18345090 rss 39387136
read initrd 102031 18447121 rss 39387136
load initrd 612288 19059409 rss 39780352
load bootparams 23351 19082760 rss 39780352
mmap runfd 34485 19117245 rss 39780352
start 22604 19139849 rss 39780352
guest start 28230316 47370165 rss 55771136
guest exit 53398 47423563 rss 55771136
cleanup 52088786 99512349 rss 37683200This shows timing at steady state from running the compiled version of vmm.js against an initrd using the init.c c program.
- guest vm allocated 70 MB RAM, times in nanoseconds, memory in bytes
KVM_CREATE_VM 16070990 16070990 rss 40271872
KVM_SET_TSS_ADDR 52270 16123260 rss 40271872
KVM_SET_IDENTITY_MAP_ADDR 38049 16161309 rss 40271872
mmap guest ram 30697 16192006 rss 40271872
KVM_SET_USER_MEMORY_REGION 117848 16309854 rss 40271872
KVM_CREATE_VCPU 515170 16825024 rss 40271872
init sreg 87838 16912862 rss 40271872
init reg 45395 16958257 rss 40271872
init cpuid 80107 17038364 rss 40271872
init msrs 29611 17067975 rss 40271872
read bzImage 409044 17477019 rss 40271872
load kernel image 1075949 18552968 rss 41975808
set bootparams 21115 18574083 rss 41975808
read initrd 3060629 21634712 rss 41975808
load initrd 8210769 29845481 rss 56393728
load bootparams 42036 29887517 rss 56393728
mmap runfd 34127 29921644 rss 56393728
start 29147 29950791 rss 56393728
guest start 28514606 58465397 rss 72384512
guest exit 53272 58518669 rss 72384512
cleanup 41390106 99908775 rss 40271872This shows timing at steady state from running the compiled version of vmm.js against an initrd using the init.js JavaScript program compiled to a static binary.
- it takes
~16 msto create the VM using theKVM_CREATEVMioctl - it takes
~0.5 msto create a VCPU bzImageis1.8 MBusing LZ4 compression and takes~0.4 msto read from/dev/shm- it takes
~1 msto set boot options and copy thebzImageinto guest memory - for the init.c guest, the lz4 compressed
initramfsis~400 KBand it takes~0.1 msto read it from/dev/shmand~0.6msto copy into guest memory - for the init.js guest the lz4 compressed
initramfsis~14 MB. this takes~3 msto read from/dev/shmand~8 msto copy into guest memory. - it takes
~28 msfrom booting the guest kernel to receiving the mmio event from the guest init.c program- this is with
lz4kernel compression. withgzipthis takes~60 msand with lzma~200 ms
- this is with
- it takes
~28 msfrom booting the guest kernel to receiving the mmio event from the guest init.js program, the same as for the init.c version - cleaning up the guest memory, unmapping memory mapped files and closing file descriptors takes
~50 ms - there are no memory leaks. if we run continually we can see memory does not increase apart from some
3-4 MBof v8 garbage that accumulates every 5 seconds or so before being freed by GC - steady state memory usage between runs is
~40 MBfor the vmm host program, written in JavaScript. When the guest runs, memory increases to~56 MBfor the init.c version and~72 MBfor the init.js version
[ 0.000000] Linux version 6.1.5 (andrew@inspiron) (gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0, GNU ld (GNU Binutils for Ubuntu) 2.38) #21 SMP Tue May 21 12:49:18 IST 2024
[ 0.000000] Command line: ro reboot=k i8042.noaux i8042.nomux i8042.nopnp i8042.nokbd noapic mitigations=off random.trust_cpu=on panic=-1 console=ttyS0,115200
[ 0.000000] Intel Spectre v2 broken microcode detected; disabling Speculation Control
[ 0.000000] Disabled fast string operations
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x008: 'MPX bounds registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x010: 'MPX CSR'
[ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
[ 0.000000] x86/fpu: xstate_offset[3]: 832, xstate_sizes[3]: 64
[ 0.000000] x86/fpu: xstate_offset[4]: 896, xstate_sizes[4]: 64
[ 0.000000] x86/fpu: Enabled xstate features 0x1f, context size is 960 bytes, using 'compacted' format.
[ 0.000000] signal: max sigframe size: 1616
[ 0.000000] BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fffe] usable
[ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000001ffffff] usable
[ 0.000000] NX (Execute Disable) protection: active
[ 0.000000] DMI not present or invalid.
[ 0.000000] tsc: Fast TSC calibration using PIT
[ 0.000000] tsc: Detected 1799.886 MHz processor
[ 0.000142] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
[ 0.000146] e820: remove [mem 0x000a0000-0x000fffff] usable
[ 0.000150] last_pfn = 0x2000 max_arch_pfn = 0x400000000
[ 0.000194] Disabled
[ 0.000195] x86/PAT: MTRRs disabled, skipping PAT initialization too.
[ 0.000208] CPU MTRRs all blank - virtualized system.
[ 0.000211] x86/PAT: Configuration [0-7]: WB WT UC- UC WB WT UC- UC
[ 0.012382] Using GB pages for direct mapping
[ 0.012524] RAMDISK: [mem 0x01f00000-0x01f61fff]
[ 0.012558] Zone ranges:
[ 0.012559] DMA [mem 0x0000000000001000-0x0000000000ffffff]
[ 0.012561] DMA32 [mem 0x0000000001000000-0x0000000001ffffff]
[ 0.012563] Normal empty
[ 0.012564] Movable zone start for each node
[ 0.012564] Early memory node ranges
[ 0.012564] node 0: [mem 0x0000000000001000-0x000000000009efff]
[ 0.012566] node 0: [mem 0x0000000000100000-0x0000000001ffffff]
[ 0.012567] Initmem setup node 0 [mem 0x0000000000001000-0x0000000001ffffff]
[ 0.012580] On node 0, zone DMA: 1 pages in unavailable ranges
[ 0.012750] On node 0, zone DMA: 97 pages in unavailable ranges
[ 0.014144] On node 0, zone DMA32: 24576 pages in unavailable ranges
[ 0.014177] smpboot: Boot CPU (id 0) not listed by BIOS
[ 0.014178] smpboot: Allowing 1 CPUs, 0 hotplug CPUs
[ 0.014183] [mem 0x02000000-0xffffffff] available for PCI devices
[ 0.014184] Booting paravirtualized kernel on bare hardware
[ 0.014186] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645519600211568 ns
[ 0.014192] setup_percpu: NR_CPUS:4 nr_cpumask_bits:1 nr_cpu_ids:1 nr_node_ids:1
[ 0.014649] percpu: Embedded 40 pages/cpu s132952 r0 d30888 u2097152
[ 0.014652] pcpu-alloc: s132952 r0 d30888 u2097152 alloc=1*2097152
[ 0.014655] pcpu-alloc: [0] 0
[ 0.014666] Built 1 zonelists, mobility grouping on. Total pages: 7824
[ 0.014668] Kernel command line: ro reboot=k i8042.noaux i8042.nomux i8042.nopnp i8042.nokbd noapic mitigations=off random.trust_cpu=on panic=-1 console=ttyS0,115200
[ 0.014742] random: crng init done
[ 0.014762] Dentry cache hash table entries: 4096 (order: 3, 32768 bytes, linear)
[ 0.014776] Inode-cache hash table entries: 2048 (order: 2, 16384 bytes, linear)
[ 0.014823] mem auto-init: stack:off, heap alloc:off, heap free:off
[ 0.014935] Memory: 18796K/32376K available (4096K kernel code, 447K rwdata, 548K rodata, 696K init, 864K bss, 13324K reserved, 0K cma-reserved)
[ 0.014987] rcu: Hierarchical RCU implementation.
[ 0.014987] rcu: RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=1.
[ 0.014989] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[ 0.014989] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
[ 0.015003] NR_IRQS: 4352, nr_irqs: 24, preallocated irqs: 16
[ 0.015257] rcu: srcu_init: Setting srcu_struct sizes based on contention.
[ 0.016464] Console: colour VGA+ 142x228
[ 0.078095] printk: console [ttyS0] enabled
[ 0.078871] APIC: ACPI MADT or MP tables are not detected
[ 0.079879] APIC: Switch to virtual wire mode setup with no configuration
[ 0.081129] Not enabling interrupt remapping due to skipped IO-APIC setup
[ 0.082557] clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x19f1bdd8caf, max_idle_ns: 440795227017 ns
[ 0.084570] Calibrating delay loop (skipped), value calculated using timer frequency.. 3599.77 BogoMIPS (lpj=7199544)
[ 0.086437] pid_max: default: 32768 minimum: 301
[ 0.087353] Mount-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
[ 0.088580] Mountpoint-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
[ 0.090210] Disabled fast string operations
[ 0.091033] x86/cpu: User Mode Instruction Prevention (UMIP) activated
[ 0.092609] Last level iTLB entries: 4KB 64, 2MB 8, 4MB 8
[ 0.093559] Last level dTLB entries: 4KB 64, 2MB 0, 4MB 0, 1GB 4
[ 0.094672] Speculative Store Bypass: Vulnerable
[ 0.095547] SRBDS: Vulnerable: No microcode
[ 0.097610] Freeing SMP alternatives memory: 8K
[ 0.098519] smpboot: CPU 0 Converting physical 6 to logical package 0
[ 0.099715] smpboot: SMP disabled
[ 0.100652] Performance Events: Skylake events, 32-deep LBR, full-width counters, Intel PMU driver.
[ 0.102348] ... version: 2
[ 0.103107] ... bit width: 48
[ 0.103909] ... generic registers: 4
[ 0.104573] ... value mask: 0000ffffffffffff
[ 0.105581] ... max period: 00007fffffffffff
[ 0.106581] ... fixed-purpose events: 3
[ 0.107334] ... event mask: 000000070000000f
[ 0.112612] rcu: Hierarchical SRCU implementation.
[ 0.113176] rcu: Max phase no-delay instances is 1000.
[ 0.113793] smp: Bringing up secondary CPUs ...
[ 0.114413] smp: Brought up 1 node, 1 CPU
[ 0.115135] smpboot: Max logical packages: 1
[ 0.115925] smpboot: Total of 1 processors activated (3599.77 BogoMIPS)
[ 0.116737] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[ 0.118532] futex hash table entries: 256 (order: 2, 16384 bytes, linear)
[ 0.121475] clocksource: Switched to clocksource tsc-early
[ 0.123013] platform rtc_cmos: registered platform RTC device (no PNP device found)
[ 0.123808] Unpacking initramfs...
[ 0.127083] Freeing initrd memory: 392K
[ 0.128007] workingset: timestamp_bits=62 max_order=13 bucket_order=0
[ 0.129972] Serial: 8250/16550 driver, 1 ports, IRQ sharing disabled
[ 0.131758] IPI shorthand broadcast: enabled
[ 0.132575] sched_clock: Marking stable (64073132, 65135839)->(141906943, -12697972)
[ 0.134153] Freeing unused kernel image (initmem) memory: 696K
[ 0.140872] Write protecting the kernel read-only data: 8192k
[ 0.141868] Freeing unused kernel image (text/rodata gap) memory: 2044K
[ 0.142796] Freeing unused kernel image (rodata/data gap) memory: 1500K
[ 0.143551] Run /init as init process
[ 0.143987] with arguments:
[ 0.144327] /init
[ 0.144627] with environment:
[ 0.144991] HOME=/
[ 0.145266] TERM=linux- handle terminal io correctly
- figure out why it hangs when we enable the IRQ chip
- add pvh boot support for loading vmlinux
- run the cpu on it's own thread
- optimize everywhere we can
- lots more...