MIPS: disable preemption whilst initialising MSA

Preemption must be disabled throughout the process of enabling the FPU,
enabling MSA & initialising the vector registers. Without doing so it
is possible to lose the FPU or MSA whilst initialising them causing
that initialisation to fail.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7307/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 4716b89543a9..22b19c275044 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1093,6 +1093,7 @@ static int enable_restore_fp_context(int msa)
 
         if (!used_math()) {
                 /* First time FP context user. */
+                preempt_disable();
                 err = init_fpu();
                 if (msa && !err) {
                         enable_msa();
@@ -1100,6 +1101,7 @@ static int enable_restore_fp_context(int msa)
                         set_thread_flag(TIF_USEDMSA);
                         set_thread_flag(TIF_MSA_CTX_LIVE);
                 }
+                preempt_enable();
                 if (!err)
                         set_used_math();
                 return err;
@@ -1139,10 +1141,11 @@ static int enable_restore_fp_context(int msa)
          * This task is using or has previously used MSA. Thus we require
          * that Status.FR == 1.
          */
+        preempt_disable();
         was_fpu_owner = is_fpu_owner();
-        err = own_fpu(0);
+        err = own_fpu_inatomic(0);
         if (err)
-                return err;
+                goto out;
 
         enable_msa();
         write_msa_csr(current->thread.fpu.msacsr);
@@ -1158,7 +1161,8 @@ static int enable_restore_fp_context(int msa)
         prior_msa = test_and_set_thread_flag(TIF_MSA_CTX_LIVE);
         if (!prior_msa && was_fpu_owner) {
                 _init_msa_upper();
-                return 0;
+
+                goto out;
         }
 
         if (!prior_msa) {
@@ -1182,6 +1186,10 @@ static int enable_restore_fp_context(int msa)
                 if (!was_fpu_owner)
                         asm volatile("ctc1 %0, $31" : : "r"(current->thread.fpu.fcr31));
         }
+
+out:
+        preempt_enable();
+
         return 0;
 }