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arm64/sve: Preserve SVE registers around kernel-mode NEON use 

Kernel-mode NEON will corrupt the SVE vector registers, due to the
way they alias the FPSIMD vector registers in the hardware.

This patch ensures that any live SVE register content for the task
is saved by kernel_neon_begin().  The data will be restored in the
usual way on return to userspace.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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>
This commit is contained in:
Dave Martin 2017-10-31 15:51:11 +00:00 committed by Will Deacon
parent 2e0f2478ea
commit 1bd3f93641
1 changed files with 4 additions and 2 deletions
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6
arch/arm64/kernel/fpsimd.c
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@ -886,8 +886,10 @@ void kernel_neon_begin(void)
__this_cpu_write(kernel_neon_busy, true); __this_cpu_write(kernel_neon_busy, true);
/* Save unsaved task fpsimd state, if any: */ /* Save unsaved task fpsimd state, if any: */
if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE)) if (current->mm) {
fpsimd_save_state(&current->thread.fpsimd_state); task_fpsimd_save();
set_thread_flag(TIF_FOREIGN_FPSTATE);
}
/* Invalidate any task state remaining in the fpsimd regs: */ /* Invalidate any task state remaining in the fpsimd regs: */
__this_cpu_write(fpsimd_last_state, NULL); __this_cpu_write(fpsimd_last_state, NULL);