GITS_BASER<n>, ITS Table Descriptors, n = 0 - 7

Indicates whether software has allocated memory for the table:

Valid	Meaning
0b0	No memory is allocated for the table. The ITS discards any writes to the interrupt translation page when either: GITS_BASER<n>.Type specifies any valid table entry type other than interrupt collections, that is, any value other than 0b100. GITS_BASER<n>.Type specifies an interrupt collection and GITS_TYPER.HCC == 0.
0b1	Memory is allocated to the table.

The reset behavior of this field is:

• On a GIC reset, this field resets to 0.

This field indicates whether an implemented register specifies a single, flat table or a two-level table where the first level contains a list of descriptors.

Indirect	Meaning
0b0	Single Level. The Size field indicates the number of pages used by the ITS to store data associated with each table entry.
0b1	Two Level. The Size field indicates the number of pages which contain an array of 64-bit descriptors to pages that are used to store the data associated with each table entry. A little endian memory order model is used.

For more information, see 'The ITS tables' in ARM® Generic Interrupt Controller Architecture Specification, GIC architecture version 3.0 and version 4.0 (ARM IHI 0069).

This field is RAZ/WI for GIC implementations that only support flat tables. If the maximum width of the scaling factor that is identified by GITS_BASER<n>.Type and the smallest page size that is supported result in a single level table that requires multiple pages, then implementing this bit as RAZ/WI is DEPRECATED.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.

Indicates the Inner Cacheability attributes of accesses to the table. The possible values of this field are:

InnerCache	Meaning
0b000	Device-nGnRnE.
0b001	Normal Inner Non-cacheable.
0b010	Normal Inner Cacheable Read-allocate, Write-through.
0b011	Normal Inner Cacheable Read-allocate, Write-back.
0b100	Normal Inner Cacheable Write-allocate, Write-through.
0b101	Normal Inner Cacheable Write-allocate, Write-back.
0b110	Normal Inner Cacheable Read-allocate, Write-allocate, Write-through.
0b111	Normal Inner Cacheable Read-allocate, Write-allocate, Write-back.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.

Read only. Specifies the type of entity that requires entries in the corresponding table. The possible values of the field are:

Type	Meaning
0b000	Unimplemented. This register does not correspond to an ITS table.
0b001	Devices. This register corresponds to an ITS table that scales with the width of the DeviceID. Only a single GITS_BASER<n> register reports this type.
0b010	vPEs. FEAT_GICv4 only. This register corresponds to an ITS table that scales with the number of vPEs in the system. The table requires (ENTRY_SIZE * N) bytes of memory, where N is the number of vPEs in the system. Only a single GITS_BASER<n> register reports this type.
0b100	Interrupt collections. This register corresponds to an ITS table that scales with the number of interrupt collections in the system. The table requires (ENTRY_SIZE * N) bytes of memory, where N is the number of interrupt collections. Not more than one GITS_BASER<n> register will report this type.

Other values are reserved.

For FEAT_GICv4p1, the registers are allocated as follows:

• GITS_BASER0.Type is 0b001 (Device).

• GITS_BASER1.Type is either 0b100 (Collection Table) or 0b000 (Unimplemented).

• GITS_BASER2.Type is either 0b010 (vPE) or 0b000 (Unimplemented).

• GITS_BASER<n>.Type, where 'n' is in the range 3 to 7, is 0b000 (Unimplemented).

For FEAT_GICv3, FEAT_GICv3p1, and FEAT_GICv4, Arm recommends that the GITS_BASER<n> use the same allocations.

Other allocations of Type values are deprecated.

Indicates the Outer Cacheability attributes of accesses to the table. The possible values of this field are:

OuterCache	Meaning
0b000	Memory type defined in InnerCache field. For Normal memory, Outer Cacheability is the same as Inner Cacheability.
0b001	Normal Outer Non-cacheable.
0b010	Normal Outer Cacheable Read-allocate, Write-through.
0b011	Normal Outer Cacheable Read-allocate, Write-back.
0b100	Normal Outer Cacheable Write-allocate, Write-through.
0b101	Normal Outer Cacheable Write-allocate, Write-back.
0b110	Normal Outer Cacheable Read-allocate, Write-allocate, Write-through.
0b111	Normal Outer Cacheable Read-allocate, Write-allocate, Write-back.

It is IMPLEMENTATION DEFINED whether this field has a fixed value or can be programmed by software. Implementing this field with a fixed value is deprecated.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.

Read-only. Specifies the number of bytes per table entry, minus one.

Physical Address. When Page_Size is 4KB or 16KB:

• Bits [51:48] of the base physical address are zero.
• This field provides bits[47:12] of the base physical address of the table.
• Bits[11:0] of the base physical address are zero.
• The address must be aligned to the size specified in the Page Size field. Otherwise the effect is CONSTRAINED UNPREDICTABLE, and can be one of the following:
  • Bits[X:12], where X is derived from the page size, are treated as zero.
  • The value of bits[X:12] are used when calculating the address of a table access.

When Page_Size is 64KB:

• Bits[47:16] of the register provide bits[47:16] of the base physical address of the table.
• Bits[15:12] of the register provide bits[51:48] of the base physical address of the table.
• Bits[15:0] of the base physical address are 0.

In implementations that support fewer than 52 bits of physical address, any unimplemented upper bits might be RAZ/WI.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.

Indicates the Shareability attributes of accesses to the table. The possible values of this field are:

Shareability	Meaning
0b00	Non-shareable.
0b01	Inner Shareable.
0b10	Outer Shareable.
0b11	Reserved. Treated as 0b00.

It is IMPLEMENTATION DEFINED whether this field has a fixed value or can be programmed by software. Implementing this field with a fixed value is deprecated.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.

The size of page that the table uses:

Page_Size	Meaning
0b00	4KB.
0b01	16KB.
0b10	64KB.
0b11	Reserved. Treated as 0b10.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.

The number of pages of physical memory allocated to the table, minus one. GITS_BASER<n>.Page_Size specifies the size of each page.

If GITS_BASER<n>.Type == 0, this field is RAZ/WI.

The reset behavior of this field is:

• On a GIC reset, this field resets to an architecturally UNKNOWN value.