[Bug 54521] New: nVMX: accurately emulate VMXON region

bugzilla-daemon
2013-02-26T15:07:23Z

Summary: nVMX: accurately emulate VMXON region
Product: Virtualization
Version: unspecified
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: enhancement
Priority: P1
Component: kvm
AssignedTo: virtualization_kvm@kernel-bugs.osdl.org
ReportedBy: nyh@math.technion.ac.il
Regression: No

According to the VMX spec, the VMXON instruction takes a "VMXON region", a 4096
byte memory region which the VMX implementation (in this case, our emulation in
nested VMX) may use for its needs.

We currently have no need to for this memory area, because when our
implementation needs to store extra data, it stores it in the vmx_vcpu
structure (in L0 memory). However, we may want to store data in guest memory in
the future - e.g. for making it easier to do live migration (see bug 53851).

In any case, according to the VMX spec, the VMXON instruction is supposed to
verify that the memory pointed by the VMXON operand is 4K aligned and has the
right physical address width, and its content has the right VMCS revision field
(copied from VMX_BASIC). We don't do this currently.

Moreover, according to the spec, VMXON needs to save this pointer, and on
VMPTRLD/VMCLEAR we need to verify that the given VMCS pointer is not the VMXON
region.

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