Re: [PATCH 1/7] KVM: userspace interface

[Anthony Liguori <aliguori@us.ibm.com>]

Sorry if I missed this, but can you provide a link to the QEMU changes?

It's hard to tell what's going on without seeing the userspace portions 
of this.

My initial impression is that you've taken the Xen approach of trying to 
use QEMU only for IO emulation.  If this is the case, it won't work long 
term.  While you can use vm86 mode for 16 bit virtualization for most 
cases, it cannot handle big real mode.  You need the ability to transfer 
down to QEMU and allow it to do emulation.

Ideally, instead of having as large of an x86 emulator in kernel space, 
you would just drop down to QEMU to do emulation as needed (doing only a 
single basic block and returning).  This would let you have a much 
reduced partial emulator in kernel space that only did the most common 
(and performance critical) instructions.

Regards,

Anthony Liguori

Avi Kivity wrote:
> This patch defines a bunch of ioctl()s on /dev/kvm.  The ioctl()s allow
> adding
> memory to a virtual machine, adding a virtual cpu to a virtual machine (at
> most one at this time), transferring control to the virtual cpu, and
> querying
> about guest pages changed by the virtual machine.
>
> Signed-off-by: Yaniv Kamay <yaniv@qumranet.com>
> Signed-off-by: Avi Kivity <avi@qumranet.com>
>
> Index: linux-2.6/include/linux/kvm.h
> ===================================================================
> --- /dev/null
> +++ linux-2.6/include/linux/kvm.h
> @@ -0,0 +1,202 @@
> +#ifndef __LINUX_KVM_H
> +#define __LINUX_KVM_H
> +
> +/*
> + * Userspace interface for /dev/kvm - kernel based virtual machine
> + *
> + * Note: this interface is considered experimental and may change without
> + *       notice.
> + */
> +
> +#include <asm/types.h>
> +#include <linux/ioctl.h>
> +
> +#ifndef __user
> +#define __user
> +#endif
> +
> +/* for KVM_CREATE_MEMORY_REGION */
> +struct kvm_memory_region {
> +    __u32 slot;
> +    __u32 flags;
> +    __u64 guest_phys_addr;
> +    __u64 memory_size; /* bytes */
> +};
> +
> +/* for kvm_memory_region::flags */
> +#define KVM_MEM_LOG_DIRTY_PAGES  1UL
> +
> +
> +#define KVM_EXIT_TYPE_FAIL_ENTRY 1
> +#define KVM_EXIT_TYPE_VM_EXIT    2
> +
> +enum kvm_exit_reason {
> +    KVM_EXIT_UNKNOWN,
> +    KVM_EXIT_EXCEPTION,
> +    KVM_EXIT_IO,
> +    KVM_EXIT_CPUID,
> +    KVM_EXIT_DEBUG,
> +    KVM_EXIT_HLT,
> +    KVM_EXIT_MMIO,
> +};
> +
> +/* for KVM_RUN */
> +struct kvm_run {
> +    /* in */
> +    __u32 vcpu;
> +    __u32 emulated;  /* skip current instruction */
> +    __u32 mmio_completed; /* mmio request completed */
> +
> +    /* out */
> +    __u32 exit_type;
> +    __u32 exit_reason;
> +    __u32 instruction_length;
> +    union {
> +        /* KVM_EXIT_UNKNOWN */
> +        struct {
> +            __u32 hardware_exit_reason;
> +        } hw;
> +        /* KVM_EXIT_EXCEPTION */
> +        struct {
> +            __u32 exception;
> +            __u32 error_code;
> +        } ex;
> +        /* KVM_EXIT_IO */
> +        struct {
> +#define KVM_EXIT_IO_IN  0
> +#define KVM_EXIT_IO_OUT 1
> +            __u8 direction;
> +            __u8 size; /* bytes */
> +            __u8 string;
> +            __u8 string_down;
> +            __u8 rep;
> +            __u8 pad;
> +            __u16 port;
> +            __u64 count;
> +            union {
> +                __u64 address;
> +                __u32 value;
> +            };
> +        } io;
> +        struct {
> +        } debug;
> +        /* KVM_EXIT_MMIO */
> +        struct {
> +            __u64 phys_addr;
> +            __u8  data[8];
> +            __u32 len;
> +            __u8  is_write;
> +        } mmio;
> +    };
> +};
> +
> +/* for KVM_GET_REGS and KVM_SET_REGS */
> +struct kvm_regs {
> +    /* in */
> +    __u32 vcpu;
> +    __u32 padding;
> +
> +    /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
> +    __u64 rax, rbx, rcx, rdx;
> +    __u64 rsi, rdi, rsp, rbp;
> +    __u64 r8,  r9,  r10, r11;
> +    __u64 r12, r13, r14, r15;
> +    __u64 rip, rflags;
> +};
> +
> +struct kvm_segment {
> +    __u64 base;
> +    __u32 limit;
> +    __u16 selector;
> +    __u8  type;
> +    __u8  present, dpl, db, s, l, g, avl;
> +    __u8  unusable;
> +    __u8  padding;
> +};
> +
> +struct kvm_dtable {
> +    __u64 base;
> +    __u16 limit;
> +    __u16 padding[3];
> +};
> +
> +/* for KVM_GET_SREGS and KVM_SET_SREGS */
> +struct kvm_sregs {
> +    /* in */
> +    __u32 vcpu;
> +    __u32 padding;
> +
> +    /* out (KVM_GET_SREGS) / in (KVM_SET_SREGS) */
> +    struct kvm_segment cs, ds, es, fs, gs, ss;
> +    struct kvm_segment tr, ldt;
> +    struct kvm_dtable gdt, idt;
> +    __u64 cr0, cr2, cr3, cr4, cr8;
> +    __u64 efer;
> +    __u64 apic_base;
> +
> +    /* out (KVM_GET_SREGS) */
> +    __u32 pending_int;
> +    __u32 padding2;
> +};
> +
> +/* for KVM_TRANSLATE */
> +struct kvm_translation {
> +    /* in */
> +    __u64 linear_address;
> +    __u32 vcpu;
> +    __u32 padding;
> +
> +    /* out */
> +    __u64 physical_address;
> +    __u8  valid;
> +    __u8  writeable;
> +    __u8  usermode;
> +};
> +
> +/* for KVM_INTERRUPT */
> +struct kvm_interrupt {
> +    /* in */
> +    __u32 vcpu;
> +    __u32 irq;
> +};
> +
> +struct kvm_breakpoint {
> +    __u32 enabled;
> +    __u32 padding;
> +    __u64 address;
> +};
> +
> +/* for KVM_DEBUG_GUEST */
> +struct kvm_debug_guest {
> +    /* int */
> +    __u32 vcpu;
> +    __u32 enabled;
> +    struct kvm_breakpoint breakpoints[4];
> +    __u32 singlestep;
> +};
> +
> +/* for KVM_GET_DIRTY_LOG */
> +struct kvm_dirty_log {
> +    __u32 slot;
> +    __u32 padding;
> +    union {
> +        void __user *dirty_bitmap; /* one bit per page */
> +        __u64 padding;
> +    };
> +};
> +
> +#define KVMIO 0xAE
> +
> +#define KVM_RUN                   _IOWR(KVMIO, 2, struct kvm_run)
> +#define KVM_GET_REGS              _IOWR(KVMIO, 3, struct kvm_regs)
> +#define KVM_SET_REGS              _IOW(KVMIO, 4, struct kvm_regs)
> +#define KVM_GET_SREGS             _IOWR(KVMIO, 5, struct kvm_sregs)
> +#define KVM_SET_SREGS             _IOW(KVMIO, 6, struct kvm_sregs)
> +#define KVM_TRANSLATE             _IOWR(KVMIO, 7, struct kvm_translation)
> +#define KVM_INTERRUPT             _IOW(KVMIO, 8, struct kvm_interrupt)
> +#define KVM_DEBUG_GUEST           _IOW(KVMIO, 9, struct kvm_debug_guest)
> +#define KVM_SET_MEMORY_REGION     _IOW(KVMIO, 10, struct kvm_memory_region)
> +#define KVM_CREATE_VCPU           _IOW(KVMIO, 11, int /* vcpu_slot */)
> +#define KVM_GET_DIRTY_LOG         _IOW(KVMIO, 12, struct kvm_dirty_log)
> +
> +#endif
>
>