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Datasheet, Volume 2

This register manages context cache. The act of writing the uppermost byte of the 
CCMD_REG with the ICC field set causes the hardware to perform the context-cache 
invalidation.

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RW-V

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Uncore

Invalidate Context-Cache (ICC) 
Software requests invalidation of context-cache by setting this 

field. Software must also set the requested invalidation 

granularity by programming the CIRG field. Software must read 

back and check the ICC field is Clear to confirm the invalidation is 

complete. Software must not update this register when this field 

is set.
Hardware clears the ICC field to indicate the invalidation request 

is complete. Hardware also indicates the granularity at which the 

invalidation operation was performed through the CAIG field. 
Software must submit a context-cache invalidation request 

through this field only when there are no invalidation requests 

pending at this remapping hardware unit.
Since information from the context-cache may be used by 

hardware to tag IOTLB entries, software must perform domain-

selective (or global) invalidation of IOTLB after the context cache 

invalidation has completed.
Hardware implementations reporting write-buffer flushing 

requirement (RWBF=1 in Capability register) must implicitly 

perform a write buffer flush before invalidating the context 

cache.

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RW

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Uncore

Context Invalidation Request Granularity (CIRG) 
Software provides the requested invalidation granularity through 

this field when setting the ICC field:
00 =  Reserved.
01 =  Global Invalidation request.
10 =  Domain-selective invalidation request. The target domain-

id must be specified in the DID field.

11 =  Device-selective invalidation request. The target source-

id(s) must be specified through the SID and FM fields, and 

the domain-id (that was programmed in the context-entry 

for these device(s)) must be provided in the DID field.

Hardware implementations may process an invalidation request 

by performing invalidation at a coarser granularity than 

requested. Hardware indicates completion of the invalidation 

request by clearing the ICC field. At this time, hardware also 

indicates the granularity at which the actual invalidation was 

performed through the CAIG field.