[Xen-devel] Is the Guest OS in non-paging protected mode when VM first execute vmlaunch?

[henanwxr <henanwxr@xxxxxxx>]

1、Is the Guest OS in non-paging protected mode when VM first execute
vmlaunch?
   If it is so, why not set it in paging protected mode, could I do this?
2、I found guest os was set in paging and protected mode in function of
construct_vmcs().
The flow is:

//Xen-4.0/arch/x86/hvm/vmx/vmcs.c
construct_vmcs()
{
  ………………..
   //here set CR0.PE
    v->arch.hvm_vcpu.guest_cr[0] = X86_CR0_PE | X86_CR0_ET;
    hvm_update_guest_cr(v, 0);
…………………
}




// Then it calls function of hvm_update_guest_cr() in
/xen/include/asm-x86/hvm.h
    static inline void hvm_update_guest_cr(struct vcpu *v, unsigned int cr)
{
    hvm_funcs.update_guest_cr(v, cr);
}



    //hvm_funcs.update_guest_cr calls function of  vmx_updata_guest_cr() 
    //in /arch/x86/hvm/vmx/vmx.c
static struct hvm_function_table __read_mostly vmx_function_table = {
    .name                 = "VMX",
    …………………………
    .update_host_cr3      = vmx_update_host_cr3,
    .update_guest_cr      = vmx_update_guest_cr,
   ……………………..
}

static void vmx_update_guest_cr(struct vcpu *v, unsigned int cr)
{
    vmx_vmcs_enter(v);

    switch ( cr )
    {
    case 0: {
        int realmode;
        unsigned long hw_cr0_mask = X86_CR0_NE;
      
 //here set CR0.PG and CR0.PE
        if ( !vmx_unrestricted_guest(v) )
         hw_cr0_mask |= X86_CR0_PG | X86_CR0_PE; 
          …………………………..
          …………………………..
         v->arch.hvm_vcpu.hw_cr[0] = v->arch.hvm_vcpu.guest_cr[0] |
hw_cr0_mask;
     //here write GUEST_CR0, is it in paging and protected mode ??   
     __vmwrite(GUEST_CR0, v->arch.hvm_vcpu.hw_cr[0]);
     __vmwrite(CR0_READ_SHADOW, v->arch.hvm_vcpu.guest_cr[0]);
      ………….       
}


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