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Deferred shadowing of segment descriptors in a virtual machine monitor for a segmented computer architecture

  • US 6,785,886 B1
  • Filed: 08/24/2000
  • Issued: 08/31/2004
  • Est. Priority Date: 05/15/1998
  • Status: Expired due to Term
First Claim
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1. In a computer system that has:

  • a memory;

    a plurality of memory segments, each corresponding to a range of the memory;

    a method for virtualizing a computer comprising the following steps;

    loading in the computer system a virtual machine monitor (VMM) and at least one virtual machine (VM) that has at least one virtual processor and is operatively connected to the VMM for running a sequence of VM instructions, the virtual machine (VM) having at least one VM descriptor table that has, as entries, VM segment descriptors, each VM segment descriptor containing memory location identifiers corresponding to a memory segment;

    in the VMM, establishing at least one VMM descriptor table, including at least one shadow descriptor table storing, for predetermined ones of the VM segment descriptors, corresponding shadow descriptors, each of the predetermined ones of the VM segment descriptors for which a shadow descriptor is stored being a shadowed descriptor;

    initializing the shadow descriptors in a desynchronized state;

    comparing the shadow descriptors with their respective corresponding shadowed VM descriptors;

    detecting a lack of correspondence between the shadow descriptor table and the corresponding VM descriptor table; and

    updating and thereby synchronizing each shadow descriptor with its respective shadowed VM descriptor, but deferring the updating of at least one shadow descriptor until the VM attempts to load the corresponding shadowed descriptor.

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