On Mon, May 22, 2023 at 06:40:59PM +0300, Dan Carpenter wrote: > 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? Reallocation is either triggered by a trap from userspace or via ptrace, as is a vector length configuration. The two cases should already be prevented from running simultaneously, and can't simultaneously perform two actions.
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