x86 Virtualization requirements (was Re: [Xen-users] intel or amd?)

[jim burns <jim_burn@xxxxxxxxxxxxx>]

On Friday 29 February 2008 09:14:01 am Michael Harley wrote:
> You can get some info from
> http://en.wikipedia.org/wiki/X86_virtualization

This link leads near the top to a link discussing requirements for an 
architecture to be virtualizable, about how efficient virtualization requires 
all sensitive instructions to be a subset of all privileged instructions (and 
therefore trapable) and from the x86 section - 
http://en.wikipedia.org/wiki/Popek_and_Goldberg_virtualization_requirements#IA-32_.28x86.29

they say:

"IA-32 (x86)

(Main article:X86 virtualization)

The IA-32 instruction set contains 17 sensitive, unprivileged instructions[3]. 
They can be categorized in two groups:

    * Sensitive register instructions: read or change sensitive registers 
and/or memory locations such as a clock register or interrupt registers:
          o SGDT, SIDT, SLDT
          o SMSW
          o PUSHF, POPF
    * Protection system instructions: reference the storage protection system, 
memory or address relocation system:
          o LAR, LSL, VERR, VERW
          o POP
          o PUSH
          o CALL, JMP, INT n, RET
          o STR
          o MOV"

MOV ??? That will really slow things down. How does xen handle this in an hvm 
domain? Does it trap all MOV instructions (even in a REP block), or does it 
just trap on illegal addresses?

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