arm64/sve: Core task context handling

[thirdparty/kernel/stable.git] / arch / arm64 / kernel / process.c

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index c15ec41e9f8457608f8d3e1c81c9db54fefbe2cb..b2adcce7bc18e628c924d009ba38190cb1bff951 100644 (file)
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -49,6 +49,7 @@
 #include <linux/notifier.h>
 #include <trace/events/power.h>
 #include <linux/percpu.h>
+#include <linux/thread_info.h>
 
 #include <asm/alternative.h>
 #include <asm/compat.h>
@@ -273,11 +274,27 @@ void release_thread(struct task_struct *dead_task)
 {
 }
 
+void arch_release_task_struct(struct task_struct *tsk)
+{
+       fpsimd_release_task(tsk);
+}
+
+/*
+ * src and dst may temporarily have aliased sve_state after task_struct
+ * is copied.  We cannot fix this properly here, because src may have
+ * live SVE state and dst's thread_info may not exist yet, so tweaking
+ * either src's or dst's TIF_SVE is not safe.
+ *
+ * The unaliasing is done in copy_thread() instead.  This works because
+ * dst is not schedulable or traceable until both of these functions
+ * have been called.
+ */
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
        if (current->mm)
                fpsimd_preserve_current_state();
        *dst = *src;
+
        return 0;
 }
 
@@ -290,6 +307,13 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 
        memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
 
+       /*
+        * Unalias p->thread.sve_state (if any) from the parent task
+        * and disable discard SVE state for p:
+        */
+       clear_tsk_thread_flag(p, TIF_SVE);
+       p->thread.sve_state = NULL;
+
        if (likely(!(p->flags & PF_KTHREAD))) {
                *childregs = *current_pt_regs();
                childregs->regs[0] = 0;