On Fri, Feb 25, 2022 at 04:59:05PM +0000, Mark Brown wrote: > The streaming mode SVE registers are represented using the same data > structures as for SVE but since the vector lengths supported and in use > may not be the same as SVE we represent them with a new type NT_ARM_SSVE. > Unfortunately we only have a single 16 bit reserved field available in > the header so there is no space to fit the current and maximum vector > length for both standard and streaming SVE mode without redefining the > structure in a way the creates a complicatd and fragile ABI. Since FFR > is not present in streaming mode it is read and written as zero. > > Setting NT_ARM_SSVE registers will put the task into streaming mode, > similarly setting NT_ARM_SVE registers will exit it. Reads that do not > correspond to the current mode of the task will return the header with > no register data. For compatibility reasons on write setting no flag for > the register type will be interpreted as setting SVE registers, though > users can provide no register data as an alternative mechanism for doing > so. > > Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
