系列文章目錄
第十七章 QEMU系統仿真的機器創建分析實例
文章目錄
- 系列文章目錄
- 第十七章 QEMU系統仿真的機器創建分析實例
- 前言
- 一、QEMU是什么？
- 二、QEMU系統仿真的機器創建分析實例
- 1.系統仿真的命令行參數
- 2.配置加速器
- configure_accelerators()
- do_configure_icount()
- 設置加速器順序
- do_configure_accelerator()
- 3.調試輸出
- 總結
前言
本文以 QEMU 8.2.2 為例，分析其作為系統仿真工具的工作過程，并為讀者展示各種 QEMU 系統仿真的啟動配置實例。
本文讀者需要具備一定的 QEMU 系統仿真使用經驗，并對 C 語言編程有一定了解。
一、QEMU是什么？
QEMU 是一個通用且開源的機器模擬器和虛擬機。
其官方主頁是：https://www.qemu.org/
二、QEMU系統仿真的機器創建分析實例
1.系統仿真的命令行參數
QEMU 作為系統仿真工具，其入口代碼在 system/main.c 文件中，初始化函數 qemu_init() 的實現在 system/vl.c 文件中。
前文完成創建目標機器的過程分析，本文將繼續后續運行過程的分析，讀者需要對 QEMU 系統啟動過程的程序代碼有所了解，相關內容可以參考《QEMU系統分析之啟動篇》系列文章。
..\qemu\8.2.2-qkd\qemu-system-x86_64.exe -cpu "Penryn" -M "q35,accel=whpx,smm=off" -m "6G" -display "sdl" -audio "sdl,model=hda" -vga "std" -L "data"
2.配置加速器
這部分代碼在 system/vl.c 文件中，實現如下：
int qemu_init(int argc, char **argv)
{
...configure_accelerators(argv[0]);
...
}
前文分析了應用當前機器設置項的過程，本文繼續完成加速器的配置過程。
configure_accelerators()
函數 configure_accelerators() 代碼如下：
static void configure_accelerators(const char *progname)
{bool init_failed = false;qemu_opts_foreach(qemu_find_opts("icount"),do_configure_icount, NULL, &error_fatal);if (QTAILQ_EMPTY(&qemu_accel_opts.head)) {char **accel_list, **tmp;if (accelerators == NULL) {/* Select the default accelerator */bool have_tcg = accel_find("tcg");bool have_kvm = accel_find("kvm");if (have_tcg && have_kvm) {if (g_str_has_suffix(progname, "kvm")) {/* If the program name ends with "kvm", we prefer KVM */accelerators = "kvm:tcg";} else {accelerators = "tcg:kvm";}} else if (have_kvm) {accelerators = "kvm";} else if (have_tcg) {accelerators = "tcg";} else {error_report("No accelerator selected and"" no default accelerator available");exit(1);}}accel_list = g_strsplit(accelerators, ":", 0);for (tmp = accel_list; *tmp; tmp++) {/** Filter invalid accelerators here, to prevent obscenities* such as "-machine accel=tcg,,thread=single".*/if (accel_find(*tmp)) {qemu_opts_parse_noisily(qemu_find_opts("accel"), *tmp, true);} else {init_failed = true;error_report("invalid accelerator %s", *tmp);}}g_strfreev(accel_list);} else {if (accelerators != NULL) {error_report("The -accel and \"-machine accel=\" options are incompatible");exit(1);}}if (!qemu_opts_foreach(qemu_find_opts("accel"),do_configure_accelerator, &init_failed, &error_fatal)) {if (!init_failed) {error_report("no accelerator found");}exit(1);}if (init_failed && !qtest_chrdev) {error_report("falling back to %s", current_accel_name());}if (icount_enabled() && !tcg_enabled()) {error_report("-icount is not allowed with hardware virtualization");exit(1);}
}
首先，如果命令行參數中有 “icount” 則調用函數 do_configure_icount() 做配置。
do_configure_icount()
代碼如下：
void icount_configure(QemuOpts *opts, Error **errp)
{const char *option = qemu_opt_get(opts, "shift");bool sleep = qemu_opt_get_bool(opts, "sleep", true);bool align = qemu_opt_get_bool(opts, "align", false);long time_shift = -1;if (!option) {if (qemu_opt_get(opts, "align") != NULL) {error_setg(errp, "Please specify shift option when using align");}return;}if (align && !sleep) {error_setg(errp, "align=on and sleep=off are incompatible");return;}if (strcmp(option, "auto") != 0) {if (qemu_strtol(option, NULL, 0, &time_shift) < 0|| time_shift < 0 || time_shift > MAX_ICOUNT_SHIFT) {error_setg(errp, "icount: Invalid shift value");return;}} else if (icount_align_option) {error_setg(errp, "shift=auto and align=on are incompatible");return;} else if (!icount_sleep) {error_setg(errp, "shift=auto and sleep=off are incompatible");return;}icount_sleep = sleep;if (icount_sleep) {timers_state.icount_warp_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,icount_timer_cb, NULL);}icount_align_option = align;if (time_shift >= 0) {timers_state.icount_time_shift = time_shift;icount_enable_precise();return;}icount_enable_adaptive();/** 125MIPS seems a reasonable initial guess at the guest speed.* It will be corrected fairly quickly anyway.*/timers_state.icount_time_shift = 3;/** Have both realtime and virtual time triggers for speed adjustment.* The realtime trigger catches emulated time passing too slowly,* the virtual time trigger catches emulated time passing too fast.* Realtime triggers occur even when idle, so use them less frequently* than VM triggers.*/timers_state.vm_clock_warp_start = -1;timers_state.icount_rt_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL_RT,icount_adjust_rt, NULL);timer_mod(timers_state.icount_rt_timer,qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) + 1000);timers_state.icount_vm_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,icount_adjust_vm, NULL);timer_mod(timers_state.icount_vm_timer,qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +NANOSECONDS_PER_SECOND / 10);
}static int do_configure_icount(void *opaque, QemuOpts *opts, Error **errp)
{icount_configure(opts, errp);return 0;
}
設置加速器順序
代碼如下：
static void configure_accelerators(const char *progname)
{
...if (QTAILQ_EMPTY(&qemu_accel_opts.head)) {char **accel_list, **tmp;if (accelerators == NULL) {/* Select the default accelerator */bool have_tcg = accel_find("tcg");bool have_kvm = accel_find("kvm");if (have_tcg && have_kvm) {if (g_str_has_suffix(progname, "kvm")) {/* If the program name ends with "kvm", we prefer KVM */accelerators = "kvm:tcg";} else {accelerators = "tcg:kvm";}} else if (have_kvm) {accelerators = "kvm";} else if (have_tcg) {accelerators = "tcg";} else {error_report("No accelerator selected and"" no default accelerator available");exit(1);}}accel_list = g_strsplit(accelerators, ":", 0);for (tmp = accel_list; *tmp; tmp++) {/** Filter invalid accelerators here, to prevent obscenities* such as "-machine accel=tcg,,thread=single".*/if (accel_find(*tmp)) {qemu_opts_parse_noisily(qemu_find_opts("accel"), *tmp, true);} else {init_failed = true;error_report("invalid accelerator %s", *tmp);}}g_strfreev(accel_list);} else {if (accelerators != NULL) {error_report("The -accel and \"-machine accel=\" options are incompatible");exit(1);}}
...
}
如果程序名后綴是 kvm 則設置 KVM 加速器優先，設置完加速器順序后完成加速器的配置。
加速器配置通過函數 do_configure_accelerator() 來完成。
do_configure_accelerator()
代碼如下：
static int do_configure_accelerator(void *opaque, QemuOpts *opts, Error **errp)
{bool *p_init_failed = opaque;const char *acc = qemu_opt_get(opts, "accel");AccelClass *ac = accel_find(acc);AccelState *accel;int ret;bool qtest_with_kvm;if (!acc) {error_setg(errp, QERR_MISSING_PARAMETER, "accel");goto bad;}qtest_with_kvm = g_str_equal(acc, "kvm") && qtest_chrdev != NULL;if (!ac) {if (!qtest_with_kvm) {error_report("invalid accelerator %s", acc);}goto bad;}accel = ACCEL(object_new_with_class(OBJECT_CLASS(ac)));object_apply_compat_props(OBJECT(accel));qemu_opt_foreach(opts, accelerator_set_property,accel,&error_fatal);/** If legacy -singlestep option is set, honour it for TCG and* silently ignore for any other accelerator (which is how this* option has always behaved).*/if (opt_one_insn_per_tb) {/** This will always succeed for TCG, and we want to ignore* the error from trying to set a nonexistent property* on any other accelerator.*/object_property_set_bool(OBJECT(accel), "one-insn-per-tb", true, NULL);}ret = accel_init_machine(accel, current_machine);if (ret < 0) {if (!qtest_with_kvm || ret != -ENOENT) {error_report("failed to initialize %s: %s", acc, strerror(-ret));}goto bad;}return 1;bad:*p_init_failed = true;return 0;
}
3.調試輸出
首先，添加跟蹤調試信息，修改后的代碼如下：
static int do_configure_accelerator(void *opaque, QemuOpts *opts, Error **errp)
{
...accel = ACCEL(object_new_with_class(OBJECT_CLASS(ac)));HUEDBG("accel=0x%llx\n", (unsigned long long int)accel);huedbg_dump_AccelClass(ac, 9);
...
}static void configure_accelerators(const char *progname)
{
...HUEDBG("accelerators=[%s]\n", accelerators);accel_list = g_strsplit(accelerators, ":", 0);
...
}int accel_init_machine(AccelState *accel, MachineState *ms)
{AccelClass *acc = ACCEL_GET_CLASS(accel);int ret;HUEDBG("accel=0x%llx\n", (unsigned long long int)accel);ms->accelerator = accel;*(acc->allowed) = true;ret = acc->init_machine(ms);if (ret < 0) {HUEDBG("\n");ms->accelerator = NULL;*(acc->allowed) = false;object_unref(OBJECT(accel));} else {HUEDBG("\n");object_set_accelerator_compat_props(acc->compat_props);}huedbg_dump_AccelClass(acc, 9);return ret;
}int qemu_init(int argc, char **argv)
{
.../** Note: uses machine properties such as kernel-irqchip, must run* after qemu_apply_machine_options.*/huedbg_flag = 1;HUEDBG("\n");configure_accelerators(argv[0]);HUEDBG("\n");huedbg_flag = 0;phase_advance(PHASE_ACCEL_CREATED);
...
}
運行后，輸出信息如下：
[21096]../system/vl.c/qemu_init(2849):
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptsList(183):<<<deep>>>=[9] list=[00007ff7ee3825c0]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptsList(185):name=[drive]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptsList(186):implied_opt_name=[(null)]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptsList(187):merge_lists=[0]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptsList(188):head=[00007ff7ee3825d8]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptsList(192):desc=[00007ff7ee3825e8]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptDesc(160):<<<deep>>>=[8] desc=[00007ff7ee3825e8]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptDesc(162):name=[(null)]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptDesc(163):type=[0]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptType(116):<<<deep>>>=[7] idx=[0]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptType(127):[0]=QEMU_OPT_STRING
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptDesc(167):help=[(null)]
[21096]../util/huedbg-option.c/huedbg_dump_QemuOptDesc(168):def_value_str=[(null)]
[21096]../system/vl.c/qemu_init(2851):
[21096]../system/vl.c/qemu_init(3824):
[21096]../system/vl.c/configure_accelerators(2419):accelerators=[whpx]
[21096]../qom/object.c/object_class_by_name(1095):enter
[21096]../qom/object.c/type_table_lookup(103):lookup type(whpx-accel) in hash table
[21096]../qom/object.c/object_class_by_name(1105):class(whpx-accel) return
[21096]../qom/object.c/type_table_lookup(103):lookup type(accel) in hash table
[21096]../qom/object.c/type_get_parent(194):parent_type(accel)
[21096]../qom/object.c/object_class_by_name(1095):enter
[21096]../qom/object.c/type_table_lookup(103):lookup type(whpx-accel) in hash table
[21096]../qom/object.c/object_class_by_name(1105):class(whpx-accel) return
[21096]../qom/object.c/object_new_with_class(818):klass->type->name=[whpx-accel]
[21096]../qom/object.c/object_new_with_type(789):try type_initialize(whpx-accel)
[21096]../qom/object.c/object_new_with_type(799):obj(whpx-accel) alloc
[21096]../qom/object.c/object_new_with_type(808):try object_initialize_with_type(whpx-accel)
[21096]../qom/object.c/object_initialize_with_type(568):obj with type(whpx-accel) enter
[21096]../qom/object.c/object_initialize_with_type(576):mapping obj(whpx-accel).class with type(whpx-accel).class
[21096]../qom/object.c/object_initialize_with_type(579):try object_class_property_init_all(whpx-accel)
[21096]../qom/object.c/object_class_property_init_all(552):obj(whpx-accel) enter
[21096]../qom/object.c/object_class_property_iter_init(1440):objclass{whpx-accel} enter
[21096]../qom/object.c/object_class_get_parent(1130):enter
[21096]../qom/object.c/type_get_parent(194):parent_type(accel)
[21096]../qom/object.c/object_class_get_parent(1138):objclass(whpx-accel) has parent(accel)
[21096]../qom/object.c/object_class_get_parent(1141):objclass(whpx-accel) return
[21096]../qom/object.c/object_class_property_iter_init(1443):objclass{whpx-accel} return
[21096]../qom/object.c/object_class_property_init_all(555):prop name=[kernel-irqchip] type=[on|off|split] desc=[Configure WHPX in-kernel irqchip] init=[0000000000000000]
[21096]../qom/object.c/object_class_get_parent(1130):enter
[21096]../qom/object.c/type_get_parent(194):parent_type(object)
[21096]../qom/object.c/object_class_get_parent(1138):objclass(accel) has parent(object)
[21096]../qom/object.c/object_class_get_parent(1141):objclass(accel) return
[21096]../qom/object.c/object_class_get_parent(1130):enter
[21096]../qom/object.c/type_get_parent(196):no parent_type
[21096]../qom/object.c/object_class_get_parent(1134):objclass(object) has no parent return
[21096]../qom/object.c/object_class_property_init_all(555):prop name=[type] type=[string] desc=[(null)] init=[0000000000000000]
[21096]../qom/object.c/object_class_property_init_all(563):obj(whpx-accel) return
[21096]../qom/object.c/object_initialize_with_type(583):try object_init_with_type(whpx-accel)
[21096]../qom/object.c/object_init_with_type(416):obj->class->type->name=[whpx-accel] ti->name=[whpx-accel] enter
[21096]../qom/object.c/type_get_parent(194):parent_type(accel)
[21096]../qom/object.c/object_init_with_type(416):obj->class->type->name=[whpx-accel] ti->name=[accel] enter
[21096]../qom/object.c/type_get_parent(194):parent_type(object)
[21096]../qom/object.c/object_init_with_type(416):obj->class->type->name=[whpx-accel] ti->name=[object] enter
[21096]../qom/object.c/object_init_with_type(427):obj->class->type->name=[whpx-accel] ti->name=[object] return
[21096]../qom/object.c/object_init_with_type(427):obj->class->type->name=[whpx-accel] ti->name=[accel] return
[21096]../qom/object.c/object_init_with_type(423):name=[whpx-accel] ti->instance_init() before
[21096]../qom/object.c/object_init_with_type(425):name=[whpx-accel] ti->instance_init() after
[21096]../qom/object.c/object_init_with_type(427):obj->class->type->name=[whpx-accel] ti->name=[whpx-accel] return
[21096]../qom/object.c/object_initialize_with_type(585):try object_post_init_with_type(whpx-accel)
[21096]../qom/object.c/object_post_init_with_type(433):obj->class->type->name=[whpx-accel] ti->name=[whpx-accel] enter
[21096]../qom/object.c/type_get_parent(194):parent_type(accel)
[21096]../qom/object.c/object_post_init_with_type(433):obj->class->type->name=[whpx-accel] ti->name=[accel] enter
[21096]../qom/object.c/type_get_parent(194):parent_type(object)
[21096]../qom/object.c/object_post_init_with_type(433):obj->class->type->name=[whpx-accel] ti->name=[object] enter
[21096]../qom/object.c/object_post_init_with_type(444):return
[21096]../qom/object.c/object_post_init_with_type(444):return
[21096]../qom/object.c/object_post_init_with_type(444):return
[21096]../qom/object.c/object_initialize_with_type(587):obj(whpx-accel) return
[21096]../qom/object.c/object_new_with_type(812):obj(whpx-accel) return
[21096]../qom/object.c/type_table_lookup(103):lookup type(accel) in hash table
[21096]../qom/object.c/type_get_parent(194):parent_type(accel)
[21096]../system/vl.c/do_configure_accelerator(2353):accel=0x1dc0cf9d320
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(76):<<<deep>>>=[9] ac=[000001dc0cf6d2e0]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(79):name=[WHPX]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(80):init_machine=[00007ff7edfa3d60]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(82):setup_post=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(83):has_memory=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(85):cpu_common_realize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(86):cpu_common_unrealize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(88):gdbstub_supported_sstep_flags=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(89):allowed=[00007ff7eefb19e9]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(91):*allowed=[0]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(93):compat_props=[0000000000000000]
[21096]../qom/object.c/type_table_lookup(103):lookup type(accel) in hash table
[21096]../qom/object.c/type_get_parent(194):parent_type(accel)
[21096]../accel/accel-system.c/accel_init_machine(40):accel=0x1dc0cf9d320
[21096]../qom/object.c/type_table_lookup(103):lookup type(machine) in hash table
[21096]../qom/object.c/type_get_parent(194):parent_type(object)
[21096]../qom/object.c/type_get_parent(196):no parent_type
[21096]../qom/object.c/type_get_parent(194):parent_type(generic-pc-machine)
[21096]../qom/object.c/type_get_parent(194):parent_type(x86-machine)
[21096]../qom/object.c/type_get_parent(194):parent_type(machine)
[21096]../target/i386/whpx/whpx-all.c/whpx_accel_init_machine(2778):mc=0x1dc0cf8b9f0,s=0x1dc0cf9d320,whpx=0x7ff7eefb1980
WHPX: setting APIC emulation mode in the hypervisor
Windows Hypervisor Platform accelerator is operational
[21096]../accel/accel-system.c/accel_init_machine(50):
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(76):<<<deep>>>=[9] ac=[000001dc0cf6d2e0]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(79):name=[WHPX]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(80):init_machine=[00007ff7edfa3d60]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(82):setup_post=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(83):has_memory=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(85):cpu_common_realize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(86):cpu_common_unrealize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(88):gdbstub_supported_sstep_flags=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(89):allowed=[00007ff7eefb19e9]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(91):*allowed=[1]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(93):compat_props=[0000000000000000]
[21096]../system/vl.c/qemu_init(3826):
注意 AccelClass 信息變化如下：
...
[21096]../system/vl.c/do_configure_accelerator(2353):accel=0x1dc0cf9d320
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(76):<<<deep>>>=[9] ac=[000001dc0cf6d2e0]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(79):name=[WHPX]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(80):init_machine=[00007ff7edfa3d60]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(82):setup_post=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(83):has_memory=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(85):cpu_common_realize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(86):cpu_common_unrealize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(88):gdbstub_supported_sstep_flags=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(89):allowed=[00007ff7eefb19e9]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(91):*allowed=[0]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(93):compat_props=[0000000000000000]
...
[21096]../accel/accel-system.c/accel_init_machine(50):
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(76):<<<deep>>>=[9] ac=[000001dc0cf6d2e0]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(79):name=[WHPX]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(80):init_machine=[00007ff7edfa3d60]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(82):setup_post=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(83):has_memory=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(85):cpu_common_realize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(86):cpu_common_unrealize=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(88):gdbstub_supported_sstep_flags=[0000000000000000]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(89):allowed=[00007ff7eefb19e9]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(91):*allowed=[1]
[21096]../util/huedbg-accel.c/huedbg_dump_AccelClass(93):compat_props=[0000000000000000]
[21096]../system/vl.c/qemu_init(3826):
未調用 accel_init_machine() 前 *allowed = 0，調用后 *allowed = 1
總結
以上分析了系統初始化過程中加速器的配置過程。
)
