?? 接著KVM虛擬機IO處理過程中Guest Vm IO處理過程(http://blog.csdn.net/dashulu/article/details/16820281),本篇文章主要描述IO從guest vm跳轉到kvm和qemu后的處理過程.
? ? 首先回顧一下kvm的啟動過程(http://blog.csdn.net/dashulu/article/details/17074675).qemu通過調用kvm提供的一系列接口來啟動kvm. qemu的入口為vl.c中的main函數,main函數通過調用kvm_init 和 machine->init來初始化kvm. 其中, machine->init會創建vcpu, 用一個線程去模擬vcpu, 該線程執行的函數為qemu_kvm_cpu_thread_fn, 并且該線程最終kvm_cpu_exec,該函數調用kvm_vcpu_ioctl切換到kvm中,下次從kvm中返回時,會接著執行kvm_vcpu_ioctl之后的代碼,判斷exit_reason,然后進行相應處理.
[cpp]?view plaincopy
int?kvm_cpu_exec(CPUState?*cpu)??{??????struct?kvm_run?*run?=?cpu->kvm_run;??????int?ret,?run_ret;????????DPRINTF("kvm_cpu_exec()\n");????????if?(kvm_arch_process_async_events(cpu))?{??????????cpu->exit_request?=?0;??????????return?EXCP_HLT;??????}????????do?{??????????if?(cpu->kvm_vcpu_dirty)?{??????????????kvm_arch_put_registers(cpu,?KVM_PUT_RUNTIME_STATE);??????????????cpu->kvm_vcpu_dirty?=?false;??????????}????????????kvm_arch_pre_run(cpu,?run);??????????if?(cpu->exit_request)?{??????????????DPRINTF("interrupt?exit?requested\n");??????????????????????????qemu_cpu_kick_self();??????????}??????????qemu_mutex_unlock_iothread();????????????run_ret?=?kvm_vcpu_ioctl(cpu,?KVM_RUN,?0);????????????qemu_mutex_lock_iothread();??????????kvm_arch_post_run(cpu,?run);????????????if?(run_ret?<?0)?{??????????????if?(run_ret?==?-EINTR?||?run_ret?==?-EAGAIN)?{??????????????????DPRINTF("io?window?exit\n");??????????????????ret?=?EXCP_INTERRUPT;??????????????????break;??????????????}??????????????fprintf(stderr,?"error:?kvm?run?failed?%s\n",??????????????????????strerror(-run_ret));??????????????abort();??????????}????????????trace_kvm_run_exit(cpu->cpu_index,?run->exit_reason);??????????switch?(run->exit_reason)?{??????????case?KVM_EXIT_IO:??????????????DPRINTF("handle_io\n");??????????????kvm_handle_io(run->io.port,????????????????????????????(uint8_t?*)run?+?run->io.data_offset,????????????????????????????run->io.direction,????????????????????????????run->io.size,????????????????????????????run->io.count);??????????????ret?=?0;??????????????break;??????????case?KVM_EXIT_MMIO:??????????????DPRINTF("handle_mmio\n");??????????????cpu_physical_memory_rw(run->mmio.phys_addr,?????????????????????????????????????run->mmio.data,?????????????????????????????????????run->mmio.len,?????????????????????????????????????run->mmio.is_write);??????????????ret?=?0;??????????????break;??????????case?KVM_EXIT_IRQ_WINDOW_OPEN:??????????????DPRINTF("irq_window_open\n");??????????????ret?=?EXCP_INTERRUPT;??????????????break;??????????case?KVM_EXIT_SHUTDOWN:??????????????DPRINTF("shutdown\n");??????????????qemu_system_reset_request();??????????????ret?=?EXCP_INTERRUPT;??????????????break;??????????case?KVM_EXIT_UNKNOWN:??????????????fprintf(stderr,?"KVM:?unknown?exit,?hardware?reason?%"?PRIx64?"\n",??????????????????????(uint64_t)run->hw.hardware_exit_reason);??????????????ret?=?-1;??????????????break;??????????case?KVM_EXIT_INTERNAL_ERROR:??????????????ret?=?kvm_handle_internal_error(cpu,?run);??????????????break;??????????default:??????????????DPRINTF("kvm_arch_handle_exit\n");??????????????ret?=?kvm_arch_handle_exit(cpu,?run);??????????????break;??????????}??????}?while?(ret?==?0);????????if?(ret?<?0)?{??????????cpu_dump_state(cpu,?stderr,?fprintf,?CPU_DUMP_CODE);??????????vm_stop(RUN_STATE_INTERNAL_ERROR);??????}????????cpu->exit_request?=?0;??????return?ret;??}?? kvm_vcpu_ioctl執行時,調用的kvm函數是virt/kvm/kvm-main.c中的kvm_vcpu_ioctl.c函數.當傳入參數為KVM_RUN時,最終會調用到vcpu_enter_guest函數, vcpu_enter_guest函數中調用了kvm_x86_ops->run(vcpu),在intel處理器架構中該函數對應的實現為vmx_vcpu_run, vmx_vcpu_run設置好寄存器狀態之后調用VM_LAUNCH或者VM_RESUME進入guest vm, 一旦發生vm exit則從此處繼續執行下去.
[cpp]?view plaincopy
static?void?__noclone?vmx_vcpu_run(struct?kvm_vcpu?*vcpu)??{??????struct?vcpu_vmx?*vmx?=?to_vmx(vcpu);??????unsigned?long?debugctlmsr;????????????vmx->__launched?=?vmx->loaded_vmcs->launched;??????asm(??????????????????"push?%%"?_ASM_DX?";?push?%%"?_ASM_BP?";"??????????"push?%%"?_ASM_CX?"?\n\t"?????????"push?%%"?_ASM_CX?"?\n\t"??????????"cmp?%%"?_ASM_SP?",?%c[host_rsp](%0)?\n\t"??????????"je?1f?\n\t"??????????"mov?%%"?_ASM_SP?",?%c[host_rsp](%0)?\n\t"??????????__ex(ASM_VMX_VMWRITE_RSP_RDX)?"\n\t"??????????"1:?\n\t"??????????????????"mov?%c[cr2](%0),?%%"?_ASM_AX?"?\n\t"??????????"mov?%%cr2,?%%"?_ASM_DX?"?\n\t"??????????"cmp?%%"?_ASM_AX?",?%%"?_ASM_DX?"?\n\t"??????????"je?2f?\n\t"??????????"mov?%%"?_ASM_AX",?%%cr2?\n\t"??????????"2:?\n\t"??????????????????"cmpl?$0,?%c[launched](%0)?\n\t"??????????????????"mov?%c[rax](%0),?%%"?_ASM_AX?"?\n\t"??????????"mov?%c[rbx](%0),?%%"?_ASM_BX?"?\n\t"??????????"mov?%c[rdx](%0),?%%"?_ASM_DX?"?\n\t"??????????"mov?%c[rsi](%0),?%%"?_ASM_SI?"?\n\t"??????????"mov?%c[rdi](%0),?%%"?_ASM_DI?"?\n\t"??????????"mov?%c[rbp](%0),?%%"?_ASM_BP?"?\n\t"??#ifdef?CONFIG_X86_64??????????"mov?%c[r8](%0),??%%r8??\n\t"??????????"mov?%c[r9](%0),??%%r9??\n\t"??????????"mov?%c[r10](%0),?%%r10?\n\t"??????????"mov?%c[r11](%0),?%%r11?\n\t"??????????"mov?%c[r12](%0),?%%r12?\n\t"??????????"mov?%c[r13](%0),?%%r13?\n\t"??????????"mov?%c[r14](%0),?%%r14?\n\t"??????????"mov?%c[r15](%0),?%%r15?\n\t"??#endif??????????"mov?%c[rcx](%0),?%%"?_ASM_CX?"?\n\t"???????????????????"jne?1f?\n\t"??????????__ex(ASM_VMX_VMLAUNCH)?"\n\t"??????????"jmp?2f?\n\t"??????????"1:?"?__ex(ASM_VMX_VMRESUME)?"\n\t"??????????"2:?"??????????????????"mov?%0,?%c[wordsize](%%"?_ASM_SP?")?\n\t"??????????"pop?%0?\n\t"??????????"mov?%%"?_ASM_AX?",?%c[rax](%0)?\n\t"??????????"mov?%%"?_ASM_BX?",?%c[rbx](%0)?\n\t"??????????__ASM_SIZE(pop)?"?%c[rcx](%0)?\n\t"??????????"mov?%%"?_ASM_DX?",?%c[rdx](%0)?\n\t"??????????"mov?%%"?_ASM_SI?",?%c[rsi](%0)?\n\t"??????????"mov?%%"?_ASM_DI?",?%c[rdi](%0)?\n\t"??????????"mov?%%"?_ASM_BP?",?%c[rbp](%0)?\n\t"??#ifdef?CONFIG_X86_64??????????"mov?%%r8,??%c[r8](%0)?\n\t"??????????"mov?%%r9,??%c[r9](%0)?\n\t"??????????"mov?%%r10,?%c[r10](%0)?\n\t"??????????"mov?%%r11,?%c[r11](%0)?\n\t"??????????"mov?%%r12,?%c[r12](%0)?\n\t"??????????"mov?%%r13,?%c[r13](%0)?\n\t"??????????"mov?%%r14,?%c[r14](%0)?\n\t"??????????"mov?%%r15,?%c[r15](%0)?\n\t"??#endif??????????"mov?%%cr2,?%%"?_ASM_AX?"???\n\t"??????????"mov?%%"?_ASM_AX?",?%c[cr2](%0)?\n\t"????????????"pop??%%"?_ASM_BP?";?pop??%%"?_ASM_DX?"?\n\t"??????????"setbe?%c[fail](%0)?\n\t"??????????".pushsection?.rodata?\n\t"??????????".global?vmx_return?\n\t"??????????"vmx_return:?"?_ASM_PTR?"?2b?\n\t"??????????".popsection"????????????:?:?"c"(vmx),?"d"((unsigned?long)HOST_RSP),??????????[launched]"i"(offsetof(struct?vcpu_vmx,?__launched)),??????????[fail]"i"(offsetof(struct?vcpu_vmx,?fail)),??????????[host_rsp]"i"(offsetof(struct?vcpu_vmx,?host_rsp)),??????????[rax]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RAX])),??????????[rbx]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RBX])),??????????[rcx]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RCX])),??????????[rdx]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RDX])),??????????[rsi]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RSI])),??????????[rdi]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RDI])),??????????[rbp]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_RBP])),??#ifdef?CONFIG_X86_64??????????[r8]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R8])),??????????[r9]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R9])),??????????[r10]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R10])),??????????[r11]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R11])),??????????[r12]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R12])),??????????[r13]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R13])),??????????[r14]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R14])),??????????[r15]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.regs[VCPU_REGS_R15])),??#endif??????????[cr2]"i"(offsetof(struct?vcpu_vmx,?vcpu.arch.cr2)),??????????[wordsize]"i"(sizeof(ulong))????????????:?"cc",?"memory"??#ifdef?CONFIG_X86_64??????????,?"rax",?"rbx",?"rdi",?"rsi"??????????,?"r8",?"r9",?"r10",?"r11",?"r12",?"r13",?"r14",?"r15"??#else??????????,?"eax",?"ebx",?"edi",?"esi"??#endif????????????);????????????if?(debugctlmsr)??????????update_debugctlmsr(debugctlmsr);????#ifndef?CONFIG_X86_64??????????loadsegment(ds,?__USER_DS);??????loadsegment(es,?__USER_DS);??#endif????????vcpu->arch.regs_avail?=?~((1?<<?VCPU_REGS_RIP)?|?(1?<<?VCPU_REGS_RSP)????????????????????|?(1?<<?VCPU_EXREG_RFLAGS)????????????????????|?(1?<<?VCPU_EXREG_CPL)????????????????????|?(1?<<?VCPU_EXREG_PDPTR)????????????????????|?(1?<<?VCPU_EXREG_SEGMENTS)????????????????????|?(1?<<?VCPU_EXREG_CR3));??????vcpu->arch.regs_dirty?=?0;????????vmx->idt_vectoring_info?=?vmcs_read32(IDT_VECTORING_INFO_FIELD);????????if?(is_guest_mode(vcpu))?{??????????struct?vmcs12?*vmcs12?=?get_vmcs12(vcpu);??????????vmcs12->idt_vectoring_info_field?=?vmx->idt_vectoring_info;??????????if?(vmx->idt_vectoring_info?&?VECTORING_INFO_VALID_MASK)?{??????????????vmcs12->idt_vectoring_error_code?=??????????????????vmcs_read32(IDT_VECTORING_ERROR_CODE);??????????????vmcs12->vm_exit_instruction_len?=??????????????????vmcs_read32(VM_EXIT_INSTRUCTION_LEN);??????????}??????}????????vmx->loaded_vmcs->launched?=?1;????????vmx->exit_reason?=?vmcs_read32(VM_EXIT_REASON);??????trace_kvm_exit(vmx->exit_reason,?vcpu,?KVM_ISA_VMX);????????vmx_complete_atomic_exit(vmx);??????vmx_recover_nmi_blocking(vmx);??????vmx_complete_interrupts(vmx);??}?? ?
?
? ? 介紹完初始化的流程,可以介紹IO在kvm和qemu中的處理流程了. 當Guest Vm進行IO操作需要訪問設備時,就會觸發vm exit 返回到vmx_vcpu_run, vmx保存好vmcs并且記錄下VM_ExIT_REASON后返回到調用該函數的vcpu_enter_guest, 在vcpu_enter_guest函數末尾調用了r = kvm_x86_ops->handle_exit(vcpu), 該函數對應于vmx_handle_exit函數(intel cpu架構對應關系可以查看vmx.c文件中static struct kvm_x86_ops vmx_x86_ops), vmx_handle_exit 調用kvm_vmx_exit_handlers[exit_reason](vcpu),該語句根據exit_reason調用不同的函數,該數據結構定義如下:
[cpp]?view plaincopy
static?int?(*const?kvm_vmx_exit_handlers[])(struct?kvm_vcpu?*vcpu)?=?{??????[EXIT_REASON_EXCEPTION_NMI]???????????=?handle_exception,??????[EXIT_REASON_EXTERNAL_INTERRUPT]??????=?handle_external_interrupt,??????[EXIT_REASON_TRIPLE_FAULT]????????????=?handle_triple_fault,??????[EXIT_REASON_NMI_WINDOW]??????????=?handle_nmi_window,??????[EXIT_REASON_IO_INSTRUCTION]??????????=?handle_io,??????[EXIT_REASON_CR_ACCESS]???????????????=?handle_cr,??????[EXIT_REASON_DR_ACCESS]???????????????=?handle_dr,??????[EXIT_REASON_CPUID]???????????????????=?handle_cpuid,??????[EXIT_REASON_MSR_READ]????????????????=?handle_rdmsr,??????[EXIT_REASON_MSR_WRITE]???????????????=?handle_wrmsr,??????[EXIT_REASON_PENDING_INTERRUPT]???????=?handle_interrupt_window,??????[EXIT_REASON_HLT]?????????????????????=?handle_halt,??????[EXIT_REASON_INVD]????????????=?handle_invd,??????[EXIT_REASON_INVLPG]??????????????=?handle_invlpg,??????[EXIT_REASON_RDPMC]???????????????????=?handle_rdpmc,??????[EXIT_REASON_VMCALL]??????????????????=?handle_vmcall,??????[EXIT_REASON_VMCLEAR]?????????????????=?handle_vmclear,??????[EXIT_REASON_VMLAUNCH]????????????????=?handle_vmlaunch,??????[EXIT_REASON_VMPTRLD]?????????????????=?handle_vmptrld,??????[EXIT_REASON_VMPTRST]?????????????????=?handle_vmptrst,??????[EXIT_REASON_VMREAD]??????????????????=?handle_vmread,??????[EXIT_REASON_VMRESUME]????????????????=?handle_vmresume,??????[EXIT_REASON_VMWRITE]?????????????????=?handle_vmwrite,??????[EXIT_REASON_VMOFF]???????????????????=?handle_vmoff,??????[EXIT_REASON_VMON]????????????????????=?handle_vmon,??????[EXIT_REASON_TPR_BELOW_THRESHOLD]?????=?handle_tpr_below_threshold,??????[EXIT_REASON_APIC_ACCESS]?????????????=?handle_apic_access,??????[EXIT_REASON_WBINVD]??????????????????=?handle_wbinvd,??????[EXIT_REASON_XSETBV]??????????????????=?handle_xsetbv,??????[EXIT_REASON_TASK_SWITCH]?????????????=?handle_task_switch,??????[EXIT_REASON_MCE_DURING_VMENTRY]??????=?handle_machine_check,??????[EXIT_REASON_EPT_VIOLATION]???????=?handle_ept_violation,??????[EXIT_REASON_EPT_MISCONFIG]???????????=?handle_ept_misconfig,??????[EXIT_REASON_PAUSE_INSTRUCTION]???????=?handle_pause,??????[EXIT_REASON_MWAIT_INSTRUCTION]???????=?handle_invalid_op,??????[EXIT_REASON_MONITOR_INSTRUCTION]?????=?handle_invalid_op,??};?? 如果是因為IO原因導致的vm exit,則調用的處理函數為handle_io,handle_io的處理可以查看(http://blog.csdn.net/fanwenyi/article/details/12748613), 該過程結束之后需要qemu去處理IO,這時候會返回到qemu, 在kvm_cpu_exec中繼續執行下去,看上面kvm_cpu_exec的代碼,如果是因為IO原因返回到qemu,會調用kvm_handle_io函數.
[cpp]?view plaincopy
switch?(run->exit_reason)?{??????????case?KVM_EXIT_IO:??????????????DPRINTF("handle_io\n");??????????????kvm_handle_io(run->io.port,????????????????????????????(uint8_t?*)run?+?run->io.data_offset,????????????????????????????run->io.direction,????????????????????????????run->io.size,????????????????????????????run->io.count);??????????????ret?=?0;??????????????break;?? kvm_handle_io調用cpu_outb, cpu_outw等指令處理IO操作.
?
? ? 假設虛擬機是用raw格式的磁盤,則IO在qemu中處理時經過的函數棧如下所示:
[cpp]?view plaincopy
#0?bdrv_aio_writev?(bs=0x55555629e9b0,?sector_num=870456,???qiov=0x555556715ab0,?nb_sectors=1,???cb=0x55555570161b?<ide_sector_write_cb>,?opaque=0x5555567157b8)??at?block.c:3408??#1?0x0000555555701960?in?ide_sector_write?(s=0x5555567157b8)??at?hw/ide/core.c:798??#2?0x00005555557047ae?in?ide_data_writew?(opaque=0x555556715740,?addr=496,???val=8995)?at?hw/ide/core.c:1907??#3?0x00005555558d9e4c?in?portio_write?(opaque=0x5555565c0670,?addr=0,???data=8995,?size=2)?at?/home/dashu/kvm/qemu/qemu-dev-zwu/ioport.c:174??#4?0x00005555558e13d5?in?memory_region_write_accessor?(mr=0x5555565c0670,???addr=0,?value=0x7fffb4dbd528,?size=2,?shift=0,?mask=65535)??at?/home/dashu/kvm/qemu/qemu-dev-zwu/memory.c:440??#5?0x00005555558e151d?in?access_with_adjusted_size?(addr=0,???value=0x7fffb4dbd528,?size=2,?access_size_min=1,?access_size_max=4,???access=0x5555558e1341?<memory_region_write_accessor>,?mr=0x5555565c0670)??at?/home/dashu/kvm/qemu/qemu-dev-zwu/memory.c:477??#6?0x00005555558e3dfb?in?memory_region_dispatch_write?(mr=0x5555565c0670,???addr=0,?data=8995,?size=2)??at?/home/dashu/kvm/qemu/qemu-dev-zwu/memory.c:984??#7?0x00005555558e7384?in?io_mem_write?(mr=0x5555565c0670,?addr=0,?val=8995,???size=2)?at?/home/dashu/kvm/qemu/qemu-dev-zwu/memory.c:1748??#8?0x000055555586a18e?in?address_space_rw?(as=0x555556216d80,?addr=496,???buf=0x7fffb4dbd670?"##",?len=2,?is_write=true)??at?/home/dashu/kvm/qemu/qemu-dev-zwu/exec.c:1968??#9?0x000055555586a474?in?address_space_write?(as=0x555556216d80,?addr=496,???buf=0x7fffb4dbd670?"##",?len=2)??at?/home/dashu/kvm/qemu/qemu-dev-zwu/exec.c:2030??#10?0x00005555558d98c9?in?cpu_outw?(addr=496,?val=8995)??at?/home/dashu/kvm/qemu/qemu-dev-zwu/ioport.c:61?? bdrv_aio_writev最終調用bdrv_co_aio_rw_vector函數, 該函數調用co = qemu_coroutine_create(bdrv_co_do_rw) 創建一個協程去執行bdrv_co_do_rw函數,bdrv_co_wo_rw函數的函數棧如下:
[cpp]?view plaincopy
#1?0x000055555563653c?in?paio_submit?(bs=0x5555562a13d0,?fd=10,?sector_num=2,???qiov=0x555556715ab0,?nb_sectors=1,???cb=0x5555556028b1?<bdrv_co_io_em_complete>,?opaque=0x555556964e30,?type=1)??at?block/raw-posix.c:825??#2?0x0000555555636659?in?raw_aio_submit?(bs=0x5555562a13d0,?sector_num=2,???qiov=0x555556715ab0,?nb_sectors=1,???cb=0x5555556028b1?<bdrv_co_io_em_complete>,?opaque=0x555556964e30,?type=1)??at?block/raw-posix.c:853??#3?0x00005555556366c9?in?raw_aio_readv?(bs=0x5555562a13d0,?sector_num=2,???qiov=0x555556715ab0,?nb_sectors=1,???cb=0x5555556028b1?<bdrv_co_io_em_complete>,?opaque=0x555556964e30)??at?block/raw-posix.c:861??#4?0x00005555556029b8?in?bdrv_co_io_em?(bs=0x5555562a13d0,?sector_num=2,???nb_sectors=1,?iov=0x555556715ab0,?is_write=false)?at?block.c:4038??#5?0x0000555555602a49?in?bdrv_co_readv_em?(bs=0x5555562a13d0,?sector_num=2,???nb_sectors=1,?iov=0x555556715ab0)?at?block.c:4055??#6?0x00005555555fed61?in?bdrv_co_do_readv?(bs=0x5555562a13d0,?sector_num=2,???nb_sectors=1,?qiov=0x555556715ab0,?flags=0)?at?block.c:2547??#7?0x00005555555fee03?in?bdrv_co_readv?(bs=0x5555562a13d0,?sector_num=2,???nb_sectors=1,?qiov=0x555556715ab0)?at?block.c:2573??#8?0x0000555555637d8c?in?raw_co_readv?(bs=0x55555629e9b0,?sector_num=2,???nb_sectors=1,?qiov=0x555556715ab0)?at?block/raw.c:47??#9?0x00005555555fed61?in?bdrv_co_do_readv?(bs=0x55555629e9b0,?sector_num=2,???nb_sectors=1,?qiov=0x555556715ab0,?flags=0)?at?block.c:2547??#10?0x00005555556023af?in?bdrv_co_do_rw??? 最終在paio_summit中會往線程池中提交一個請求thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque), 由調度器去執行aio_worker函數,aio_worker是真正做IO操作的函數,它通過pwrite和pread去讀取磁盤.
?
? ? 當qemu完成IO操作后,會在kvm_cpu_exec函數的循環中,調用kvm_vcpu_ioctl重新進入kvm.
? ? 以上闡述了IO操作在kvm和qemu中處理的整個過程.
?
參考資料:
1. kvm代碼解析連載(二):io的虛擬化:http://blog.csdn.net/fanwenyi/article/details/12748613
總結
以上是生活随笔為你收集整理的KVM虚拟机IO处理过程(二) ----QEMU/KVM I/O 处理过程的全部內容，希望文章能夠幫你解決所遇到的問題。
如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。
