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PMBIDR_EL1, Profiling Buffer ID Register

The PMBIDR_EL1 characteristics are:

Purpose

Provides information to software as to whether the buffer can be programmed at the current Exception level.

Configuration

This register is present only when SPE is implemented. Otherwise, direct accesses to PMBIDR_EL1 are UNDEFINED.

Attributes

PMBIDR_EL1 is a 64-bit register.

Field descriptions

The PMBIDR_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
00000000000000000000000000FPAlign
313029282726252423222120191817161514131211109876543210

Bits [63:6]

Reserved, RES0.

F, bit [5]

Flag Updates. Defines whether the address translation performed by the Profiling Buffer manages the Access Flag and dirty state.

FMeaning
0b0

Hardware management of the Access Flag and dirty state for accesses made by the Statistical Profiling Extension is always disabled for all translation stages.

0b1

Hardware management for the Access Flag and dirty state for accesses made by the Statistical Profiling Extension is controlled in the same way as explicit memory accesses in the owning translation regime.

If hardware management of the Access Flag is disabled for a stage of translation, an access to Page or Block with the Access flag bit not set in the descriptor will generate an Access Flag fault.

If hardware management of the dirty state is disabled for a stage of translation, an access to a Page or Block will ignore the Dirty Bit Modifier in the descriptor might generate a Permission fault, depending on the values of the access permission bits in the descriptor.

P, bit [4]

When ARMv8.4-SecEL2 is implemented:

Programming not allowed. The Profiling Buffer is owned by a higher Exception level or the other Security state.

PMeaning
0b0

Profiling Buffer is owned by the current or a lower Exception level in the current Security state.

0b1

Profiling Buffer is owned by a higher Exception level or the other Security state.

The value read from this field depends on the current Exception level and the values of MDCR_EL3.NSPB and MDCR_EL2.E2PB:

  • If MDCR_EL3.NSPB == 0b00 or MDCR_EL3.NSPB == 0b01, this bit reads as one from Non-secure EL2 and Non-secure EL1.
  • If MDCR_EL3.NSPB == 0b10 or MDCR_EL3.NSPB == 0b11, this bit reads as one from Secure EL1 and, if Secure EL2 is implemented and enabled, Secure EL2.
  • If MDCR_EL2.E2PB == 0b00, this bit reads as one from Non-secure EL1, and if Secure EL2 is implemented and enabled, also from Secure EL1.
  • Otherwise, this bit reads as zero.


From Armv8.1:

Programming not allowed. The Profiling Buffer is owned by a higher Exception level or the other Security state.

PMeaning
0b0

Profiling Buffer is owned by the current or a lower Exception level in the current Security state.

0b1

Profiling Buffer is owned by a higher Exception level or the other Security state.

The value read from this field depends on the current Exception level and the values of MDCR_EL3.NSPB and MDCR_EL2.E2PB:

  • If MDCR_EL3.NSPB == 0b00 or MDCR_EL3.NSPB == 0b01, this bit reads as one from EL2 and Non-secure EL1.
  • If MDCR_EL3.NSPB == 0b10 or MDCR_EL3.NSPB == 0b11, this bit reads as one from Secure EL1.
  • If MDCR_EL2.E2PB == 0b00, this bit reads as one from Non-secure EL1.
  • Otherwise, this bit reads as zero.


Otherwise:

Reserved, RES0.

Align, bits [3:0]

Defines the minimum alignment constraint for PMBPTR_EL1. If this field is non-zero, then the PE must pad every record up to a multiple of this size.

AlignMeaning
0b0000

Byte

0b0001

Halfword.

0b0010

Word.

0b0011

Doubleword.

0b0100

16 Bytes.

0b0101

32 Bytes.

0b0110

64 Bytes.

0b0111

128 Bytes.

0b1000

256 Bytes.

0b1001

512 Bytes.

0b1010

1KB.

0b1011

2KB.

For more information, see Restrictions on the current write pointer.

Accessing the PMBIDR_EL1

Accesses to this register use the following encodings:

MRS <Xt>, PMBIDR_EL1

op0CRnop1op2CRm
0b110b10010b0000b1110b1010
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    return PMBIDR_EL1;
elsif PSTATE.EL == EL2 then
    return PMBIDR_EL1;
elsif PSTATE.EL == EL3 then
    return PMBIDR_EL1;
              


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