[Xen-devel] calling the VMX instructions from HVM guest application

["Praveen Kushwaha" <praveen.kushwaha@xxxxxxxxxxx>]

 

Hi

        Since the xen(Intel) provide the VMX instruction set (like VMPTRLD, VMREAD, VMWRITE, VMCLEAR VMCALL  etc.) to manage the VMCS.

        I have some queries regarding these instructions:

 

1.      Can an application in HVM guest  call these VMX instructions? If yes how to call these VMX instructions, is it through the hyper calls or through other mechanism?

2.      Is VMCS structure is updated by the processor automatically in case VMexit happens ? Suppose VMExit operation caused due to VMcall then  

       Will the VMCS structure will be updated automatically(i.e. Guest state information is saved on VMCS) ? can the application in HVM guest also

       store some information on VMCS?

3.      what are the other way to pass information from HVM guest to hypervisor. Though there is VMWRITE instruction is there, but how actually it works? I mean to say that , if VMWRITE instruction will be called then VMExit will happen. Then how exactly to pass information to hypervisor using VMCS?

           

            Above of some questions might not be intelligent enough. If anyone has  information regarding it please reply.

 

Thanks,

Praveen Kushwaha

 

 

 

 

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