arm64/sve: Support vector length resetting for new processes

It's desirable to be able to reset the vector length to some sane
default for new processes, since the new binary and its libraries
may or may not be SVE-aware.

This patch tracks the desired post-exec vector length (if any) in a
new thread member sve_vl_onexec, and adds a new thread flag
TIF_SVE_VL_INHERIT to control whether to inherit or reset the
vector length.  Currently these are inactive.  Subsequent patches
will provide the capability to configure them.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index e2f575dbdddd..c6fddb005dc2 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -107,6 +107,7 @@ struct thread_struct {
         struct fpsimd_state     fpsimd_state;
         void                    *sve_state;     /* SVE registers, if any */
         unsigned int            sve_vl;         /* SVE vector length */
+        unsigned int            sve_vl_onexec;  /* SVE vl after next exec */
         unsigned long           fault_address;  /* fault info */
         unsigned long           fault_code;     /* ESR_EL1 value */
         struct debug_info       debug;          /* debugging */