The principle of KVM virtualization

The KVM structure contains information such as Vcpus, memory, and Apic,irq,mmu,event event management. The information in this structure is primarily used inside a KVM virtual machine to track the state of a virtual machine.

For a KVM, it corresponds to a thread.

KVM takes full advantage of hardware virtualization technology to view information via Cat/proc/cpuinfo, and if it is an Intel processor, load Kvm-intel.ko

The user state creates a virtual machine that is set up and managed by the IOCTL to the/DEV/KVM character device.

struct KVM {

spinlock_t Mmu_lock;

spinlock_t Requests_lock;

struct Rw_semaphore slots_lock;

struct Mm_struct *mm; /* Userspace tied to this VM */

int nmemslots;

struct Kvm_memory_slot memslots[kvm_memory_slots +

Kvm_private_mem_slots];

#ifdef config_kvm_apic_architecture

U32 bsp_vcpu_id;

struct KVM_VCPU *bsp_vcpu;

#endif

struct KVM_VCPU *vcpus[kvm_max_vcpus];

atomic_t Online_vcpus;

struct List_head vm_list;

struct mutex lock;

struct Kvm_io_bus Mmio_bus;

struct Kvm_io_bus Pio_bus;

#ifdef CONFIG_HAVE_KVM_EVENTFD

struct {

spinlock_t lock;

struct List_head items;

} Irqfds;

struct List_head Ioeventfds;

#endif

struct KVM_VM_STAT stat;

struct Kvm_arch arch;

atomic_t Users_count;

#ifdef Kvm_coalesced_mmio_page_offset

struct Kvm_coalesced_mmio_dev *coalesced_mmio_dev;

struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;

#endif

struct Mutex irq_lock;

#ifdef config_have_kvm_irqchip

struct List_head irq_routing; /* of Kvm_kernel_irq_routing_entry * *

struct Hlist_head mask_notifier_list;

#endif

#ifdef Kvm_arch_want_mmu_notifier

struct Mmu_notifier mmu_notifier;

unsigned long mmu_notifier_seq;

Long Mmu_notifier_count;

#endif

};

struct Kvm_vm_stat stat; is the run-time state information of the page table, the MMU, and so on in the KVM virtual machine.

All members in the Kvm_x86_ops struct are function pointers, and in the two different modules of the Kvm-intel.ko and Kvm-amd.ko, different functions are made for the respective systems. The KVM subsystem code will perform the actual hardware operation through the struct function.

For KVM FD, the KVM_CREATE_VCPU command Word can be used to create the KVM Vcpus, and the operation to obtain the VCPU_FD,VCPU_FD is mainly included in Kvm_vcpu_fops, Kvm_vcpu_fops implementation is as follows:

static struct File_operations Kvm_vcpu_fops = {

. Release = Kvm_vcpu_release,

. Unlocked_ioctl = Kvm_vcpu_ioctl,

. Compat_ioctl = Kvm_vcpu_ioctl,

. mmap = Kvm_vcpu_mmap,

};

The principle of KVM virtualization