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Diffstat (limited to 'Documentation/arch/arm64/sme.rst')
| -rw-r--r-- | Documentation/arch/arm64/sme.rst | 22 |
1 files changed, 6 insertions, 16 deletions
diff --git a/Documentation/arch/arm64/sme.rst b/Documentation/arch/arm64/sme.rst index b2fa01f85cb5..583f2ee9cb97 100644 --- a/Documentation/arch/arm64/sme.rst +++ b/Documentation/arch/arm64/sme.rst @@ -69,8 +69,8 @@ model features for SME is included in Appendix A. vectors from 0 to VL/8-1 stored in the same endianness invariant format as is used for SVE vectors. -* On thread creation TPIDR2_EL0 is preserved unless CLONE_SETTLS is specified, - in which case it is set to 0. +* On thread creation PSTATE.ZA and TPIDR2_EL0 are preserved unless CLONE_VM + is specified, in which case PSTATE.ZA is set to 0 and TPIDR2_EL0 is set to 0. 2. Vector lengths ------------------ @@ -81,17 +81,7 @@ The ZA matrix is square with each side having as many bytes as a streaming mode SVE vector. -3. Sharing of streaming and non-streaming mode SVE state ---------------------------------------------------------- - -It is implementation defined which if any parts of the SVE state are shared -between streaming and non-streaming modes. When switching between modes -via software interfaces such as ptrace if no register content is provided as -part of switching no state will be assumed to be shared and everything will -be zeroed. - - -4. System call behaviour +3. System call behaviour ------------------------- * On syscall PSTATE.ZA is preserved, if PSTATE.ZA==1 then the contents of the @@ -112,10 +102,10 @@ be zeroed. exceptions for execve() described in section 6. -5. Signal handling +4. Signal handling ------------------- -* Signal handlers are invoked with streaming mode and ZA disabled. +* Signal handlers are invoked with PSTATE.SM=0, PSTATE.ZA=0, and TPIDR2_EL0=0. * A new signal frame record TPIDR2_MAGIC is added formatted as a struct tpidr2_context to allow access to TPIDR2_EL0 from signal handlers. @@ -241,7 +231,7 @@ prctl(PR_SME_SET_VL, unsigned long arg) length, or calling PR_SME_SET_VL with the PR_SME_SET_VL_ONEXEC flag, does not constitute a change to the vector length for this purpose. - * Changing the vector length causes PSTATE.ZA and PSTATE.SM to be cleared. + * Changing the vector length causes PSTATE.ZA to be cleared. Calling PR_SME_SET_VL with vl equal to the thread's current vector length, or calling PR_SME_SET_VL with the PR_SME_SET_VL_ONEXEC flag, does not constitute a change to the vector length for this purpose. |