On Thu, May 18, 2023 at 10:52:31AM +0900, Mark Brown wrote:
> > When we call sme_alloc() it will say the buffer is already allocated
> > and just zero out what we need for "vl", but the existing buffer is too
> > small.
>
> If we are setting the SVE vector length we do not need to reallocate the
> SME state since the size of the data stored in the sme_state buffer is
> influenced only by the SME vector length, not the SVE vector length. We
> unconditionally free the SVE state (causing it to be reallocated when
> needed) since the size needed for it depends on both vector lengths.
arch/arm64/kernel/fpsimd.c
909 /*
910 * Force reallocation of task SVE and SME state to the correct
911 * size on next use:
912 */
913 sve_free(task);
^^^^^^^^^^^^^^
Sure, this forces a reallocation. But what prevents it from happening
before we reach the task_set_vl() line?
914 if (system_supports_sme() && type == ARM64_VEC_SME)
915 sme_free(task);
916
917 task_set_vl(task, type, vl);
918
919 out:
920 update_tsk_thread_flag(task, vec_vl_inherit_flag(type),
921 flags & PR_SVE_VL_INHERIT);
922
923 return 0;
regards,
dan carpenter
