Difference between revisions of "Power ISA/Privilege States"

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* ultravisor privileged state
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== States ==
* hypervisor privileged state
 
* privileged state / supervisor mode
 
* problem state / user mode
 
  
At the moment very little information exists about the ultravisor state. It is not mentioned in Power ISA version 2.07 documents at all, and version 3.0B only mentions it as a possible classification for instructions:
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=== Ultravisor State ===
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At the moment very little information exists about the Ultravisor State. It is not mentioned in Power ISA version 2.07 documents at all, and version 3.0B only mentions it as a possible privilege of instructions. There is no official documentation of a ''UV'' - ''Ultravisor State'' [[Machine State Register]] bit, although some source code does reference its existence.<ref>https://patchwork.ozlabs.org/patch/719952/</ref>
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=== Hypervisor State ===
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Hypervisor State was introduced in POWER4, although for some time it was not included in documentation, appearing only as a ''reserved'' bit in the Machine State Register.<ref>Kerr, Jeremy. [https://www.youtube.com/watch?v=DigNr08GVss OpenPOWER: building an open-source software stack from bare metal] (video). Linux.conf.au 2015</ref> It is indicated by the [[Machine State Register#Bit_3_-_Hypervisor_State_.28HV.29|HV (bit 3)]] of the Machine State Register
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=== Privileged State ===
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Also called Supervisor Mode
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=== Problem State ===
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Also called User Mode
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== Instruction Classification ==
  
 
{| class="wikitable sortable"
 
{| class="wikitable sortable"
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|an instruction that can be executed only in ultravisor state
 
|an instruction that can be executed only in ultravisor state
 
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|}
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== References ==
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<references/>

Revision as of 02:46, 21 January 2018

States

Ultravisor State

At the moment very little information exists about the Ultravisor State. It is not mentioned in Power ISA version 2.07 documents at all, and version 3.0B only mentions it as a possible privilege of instructions. There is no official documentation of a UV - Ultravisor State Machine State Register bit, although some source code does reference its existence.[1]

Hypervisor State

Hypervisor State was introduced in POWER4, although for some time it was not included in documentation, appearing only as a reserved bit in the Machine State Register.[2] It is indicated by the HV (bit 3) of the Machine State Register

Privileged State

Also called Supervisor Mode

Problem State

Also called User Mode

Instruction Classification

Privilege Classification of Instructions in Power ISA
Code 2.07 3.0B Description
P Yes Yes a privileged instruction.
O Yes Yes an instruction that is treated as privileged or nonprivileged (or hypervisor, for mtspr), depend-

ing on the SPR or PMR number.

PI No Yes an instruction that is illegal in privileged state.
H Yes Yes an instruction that can be executed only in hypervisor state
PH Yes No a hypervisor privileged instruction if Category Embedded.Hypervisor is implemented; otherwise

denotes a privileged instruction.

M Yes No an instruction that is treated as privileged or nonprivileged, depending on the value of the UCLE

bit in the MSR

U No Yes an instruction that can be executed only in ultravisor state

References