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How to analyze the initialization of KVM hardware virtualization in qemu? I believe many inexperienced people don't know what to do about it. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

Initialization Analysis of KVM hardware Virtualization in qemu 2014-04-25 14:38:38

Classification: virtualization

1. Pass in the-enable-kvm parameter to enable KVM hardware virtualization support:

In the file qemu-options.hx, the parameter-enable-kvm is defined as follows:

DEF ("enable-kvm", 0, QEMU_OPTION_enable_kvm,\

"- enable-kvm enable KVM full virtualization support\ n", QEMU_ARCH_ALL)

STEXI

@ item-enable-kvm

@ findex-enable-kvm

Enable KVM full virtualization support. This option is only available

If KVM support is enabled when compiling.

ETEXI

Analysis of the corresponding parameters in the 2.main function

Int main (int argc, char * argv, char * * envp)

{

/ * second pass of option parsing * /

Optind = 1

For (;;) {

.

Case QEMU_OPTION_enable_kvm:

Olist = qemu_find_opts ("machine")

Qemu_opts_parse (olist, "accel=kvm", 0)

Break

.

}

.

Os_daemonize ()

.

Configure_accelerator (machine)

.

}

(gdb) p * machine

$46 = {name = 0x555555a17666 "pc-i440fx-2.0", alias = 0x555555a17674 "pc"

Desc = 0x555555a175d8 "Standard PC (i440FX + PIIX, 1996)", init = 0x5555558c2e2c, reset = 0

Hot_add_cpu = 0x5555558c1061, kvm_type = 0, block_default_type = IF_IDE, max_cpus = 255, no_serial = 0

No_parallel = 0, use_virtcon = 0, use_sclp = 0, no_floppy = 0, no_cdrom = 0, no_sdcard = 0, is_default = 1

Default_machine_opts = 0x555555a17677 "firmware=bios-256k.bin", default_boot_order = 0x555555a1768e "cad", compat_props = 0x0

Next = 0x0, hw_version = 0x0}

/ / qemu supports four execution methods: tcg, xen, kvm, and qtest

Static struct {

Const char * opt_name

Const char * name

Int (* available) (void)

Int (* init) (QEMUMachine *)

Bool * allowed

} accel_list [] = {

{"tcg", "tcg", tcg_available, tcg_init, & tcg_allowed}

{"xen", "Xen", xen_available, xen_init, & xen_allowed}

{"kvm", "KVM", kvm_available, kvm_init, & kvm_allowed}

{"qtest", "QTest", qtest_available, qtest_init_accel, & qtest_allowed}

}

/ / parse the parameters and initialize the relevant modules

Static int configure_accelerator (QEMUMachine * machine)

{

Const char * p

Char buf [10]

Int i, ret

Bool accel_initialised = false

Bool init_failed = false

/ / when there is no-enable-kvm parameter, the tcg simulated by software is used by default.

P = qemu_opt_get (qemu_get_machine_opts (), "accel")

If (p = = NULL) {

/ * Use the default "accelerator", tcg * /

P = "tcg"

}

While (! accel_initialised & & * p! ='\ 0') {

If (* p = =':') {

Pendant +

}

P = get_opt_name (buf, sizeof (buf), p,':')

For (I = 0; I)

< ARRAY_SIZE(accel_list); i++) { if (strcmp(accel_list[i].opt_name, buf) == 0) { if (!accel_list[i].available()) { printf("%s not supported for this target\n", accel_list[i].name); continue; } *(accel_list[i].allowed) = true; ret = accel_list[i].init(machine); if (ret < 0) { init_failed = true; fprintf(stderr, "failed to initialize %s: %s\n", accel_list[i].name, strerror(-ret)); *(accel_list[i].allowed) = false; } else { accel_initialised = true; } break; } } if (i == ARRAY_SIZE(accel_list)) { fprintf(stderr, "\"%s\" accelerator does not exist.\n", buf); } } if (!accel_initialised) { if (!init_failed) { fprintf(stderr, "No accelerator found!\n"); } exit(1); } if (init_failed) { fprintf(stderr, "Back to %s accelerator.\n", accel_list[i].name); } return !accel_initialised; } 3.kvm_init int kvm_init(QEMUMachine *machine) { ...... s->

Fd = qemu_open ("/ dev/kvm", O_RDWR)

If (s-> fd = =-1) {

Fprintf (stderr, "Could not access KVM kernel module:% m\ n")

Ret =-errno

Goto err

}

/ / matches the version of the kvm kernel module. It will not be supported if the version is too old or too new.

Ret = kvm_ioctl (s, KVM_GET_API_VERSION, 0)

If (ret

< KVM_API_VERSION) { if (ret >

0) {

Ret =-EINVAL

}

Fprintf (stderr, "kvm version too old\ n")

Goto err

}

If (ret > KVM_API_VERSION) {

Ret =-EINVAL

Fprintf (stderr, "kvm version not supported\ n")

Goto err

}

.

/ * check the vcpu limits * /

Soft_vcpus_limit = kvm_recommended_vcpus (s); / / get the number of vcpu recommended by the kvm kernel

Hard_vcpus_limit = kvm_max_vcpus (s); / / get the maximum number of vcpu available for the kvm kernel

.

Do {

Ret = kvm_ioctl (s, KVM_CREATE_VM, type); / / create a VM

} while (ret = =-EINTR)

.

Ret = kvm_arch_init (s)

If (ret

< 0) { goto err; } ret = kvm_irqchip_create(s); if (ret < 0) { goto err; } kvm_state = s; memory_listener_register(&kvm_memory_listener, &address_space_memory); memory_listener_register(&kvm_io_listener, &address_space_io); s->

Many_ioeventfds = kvm_check_many_ioeventfds ()

Cpu_interrupt_handler = kvm_handle_interrupt

Return 0

.

}

After reading the above, have you mastered how to analyze the initialization of KVM hardware virtualization in qemu? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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