[PATCH v2 5/7] arm64/fpsimd: Load FP state based on recorded data type

[Mark Brown]

Now that we are recording the type of floating point register state we
are saving when we save it we can use that information when we load to
decide which register state is required and bring the TIF_SVE state into
sync with the loaded register state.

The SME state detauls are already recorded directly in the saved
SVCR and handled based on the information there.

Since we are not changing any of the save paths there should be no
functional change from this patch, further patches will make use of this
to optimise and clarify the code.

Signed-off-by: Mark Brown <broonie at kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index ebe66d8c66e8..f14452b7a629 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -391,11 +391,38 @@ static void task_fpsimd_load(void)
 	WARN_ON(!system_supports_fpsimd());
 	WARN_ON(!have_cpu_fpsimd_context());
 
-	/* Check if we should restore SVE first */
-	if (IS_ENABLED(CONFIG_ARM64_SVE) && test_thread_flag(TIF_SVE)) {
-		sve_set_vq(sve_vq_from_vl(task_get_sve_vl(current)) - 1);
-		restore_sve_regs = true;
-		restore_ffr = true;
+	if (system_supports_sve()) {
+		switch (current->thread.fp_type) {
+		case FP_STATE_FPSIMD:
+			/* Stop tracking SVE for this task until next use. */
+			if (test_and_clear_thread_flag(TIF_SVE))
+				sve_user_disable();
+			break;
+		case FP_STATE_SVE:
+			/*
+			 * A thread with SVE state should either be in
+			 * streaming mode or already have SVE enabled.
+			 */
+			if (!thread_sm_enabled(&current->thread) &&
+			    !WARN_ON_ONCE(!test_and_set_thread_flag(TIF_SVE)))
+				sve_user_enable();
+
+			sve_set_vq(sve_vq_from_vl(task_get_sve_vl(current)) - 1);
+			restore_sve_regs = true;
+			restore_ffr = true;
+			break;
+		default:
+			/*
+			 * This should never happen, we should always
+			 * record what we saved when we save. We
+			 * always at least have the memory allocated
+			 * for FPSMID registers so try that and hope
+			 * for the best.
+			 */
+			WARN_ON_ONCE(1);
+			clear_thread_flag(TIF_SVE);
+			break;
+		}
 	}
 
 	/* Restore SME, override SVE register configuration if needed */
-- 
2.30.2