Index

SMSTOP

Disables access to Streaming SVE mode and SME architectural state.

SMSTOP exits Streaming SVE mode, and disables the SME ZA storage.

SMSTOP SM exits Streaming SVE mode, but does not disable the SME ZA storage.

SMSTOP ZA disables the SME ZA storage, but does not cause an exit from Streaming SVE mode.

This is an alias of MSR (immediate). This means:

System
(FEAT_SME)

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 1 0 1 0 1 0 1 0 0 0 0 0 0 1 1 0 1 0 0 0 x x 0 0 1 1 1 1 1 1 1
op1 CRm op2

SMSTOP {<option>}

is equivalent to

MSR <pstatefield>, #0

and is always the preferred disassembly.

Assembler Symbols

<option>

Is an optional mode, encoded in CRm<2:1>:

CRm<2:1> <option>
00 RESERVED
01 SM
10 ZA
11 [no specifier]
<pstatefield>

Is a PSTATE field name. For the MSR instruction, this is encoded in op1:op2:CRm:

op1 op2 CRm <pstatefield> Architectural Feature
000 00x xxxx SEE PSTATE -
000 010 xxxx SEE PSTATE -
000 011 xxxx UAO FEAT_UAO
000 100 xxxx PAN FEAT_PAN
000 101 xxxx SPSel -
000 11x xxxx RESERVED -
001 000 000x ALLINT FEAT_NMI
001 000 001x PM FEAT_EBEP
001 000 01xx RESERVED -
001 000 1xxx RESERVED -
001 001 xxxx RESERVED -
001 01x xxxx RESERVED -
001 1xx xxxx RESERVED -
010 xxx xxxx RESERVED -
011 000 xxxx RESERVED -
011 001 xxxx SSBS FEAT_SSBS
011 010 xxxx DIT FEAT_DIT
011 011 000x RESERVED -
011 011 001x SVCRSM FEAT_SME
011 011 010x SVCRZA FEAT_SME
011 011 011x SVCRSMZA FEAT_SME
011 011 1xxx RESERVED -
011 100 xxxx TCO FEAT_MTE
011 101 xxxx RESERVED -
011 110 xxxx DAIFSet -
011 111 xxxx DAIFClr -
1xx xxx xxxx RESERVED -
For the SMSTART and SMSTOP aliases, this is encoded in "CRm<2:1>", where 0b01 specifies SVCRSM, 0b10 specifies SVCRZA, and 0b11 specifies SVCRSMZA.

Operation

The description of MSR (immediate) gives the operational pseudocode for this instruction.