commit baeeb9402331fa7588aa3214086ec11477ae587d
author Mark Brown <broonie@kernel.org> Wed Nov 06 16:40:34 2024 +0000
committer Mark Brown <broonie@kernel.org> Wed Nov 06 16:40:34 2024 +0000
tree 9511d7038f24fd92f8d581fc5092b205ca821e95
parent 12329b144a1c0e115c30a937599de7e033a1d4e3

arm64/fp: Don't corrupt FPMR when streaming mode changes

When we enter or exit streaming more FPMR is reset to 0.  This means
that when restoring the floating point state from memory we need to
restore FPMR after we restore SVCR, otherwise if we are entering or
exiting streaming mode as part of loading the new state the value of
FPMR will be corrupted.

Fixes: 203f2b95a882 ("arm64/fpsimd: Support FEAT_FPMR")
Signed-off-by: Mark Brown <broonie@kernel.org>

arch/arm64/kernel/fpsimd.c

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 77006df..b26d93a 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -359,9 +359,6 @@ static void task_fpsimd_load(void)
 	WARN_ON(preemptible());
 	WARN_ON(test_thread_flag(TIF_KERNEL_FPSTATE));
 
-	if (system_supports_fpmr())
-		write_sysreg_s(current->thread.uw.fpmr, SYS_FPMR);
-
 	if (system_supports_sve() || system_supports_sme()) {
 		switch (current->thread.fp_type) {
 		case FP_STATE_FPSIMD:
@@ -413,6 +410,9 @@ static void task_fpsimd_load(void)
 			restore_ffr = system_supports_fa64();
 	}
 
+	if (system_supports_fpmr())
+		write_sysreg_s(current->thread.uw.fpmr, SYS_FPMR);
+
 	if (restore_sve_regs) {
 		WARN_ON_ONCE(current->thread.fp_type != FP_STATE_SVE);
 		sve_load_state(sve_pffr(&current->thread),