Per commit:
0cecca9d03c964ab ("x86/fpu: Eager switch PKRU state")
... switch_fpu_state() is trying to distinguish user threads from
kthreads, such that kthreads consistently use init_pkru_value. It does
do by looking at current->mm.
In general, a non-NULL current->mm doesn't imply that current is a
kthread, as kthreads can install an mm via use_mm(), and so it's
preferable to use is_kthread() to determine whether a thread is a
kthread.
For consistency, let's use is_kthread() here.
Signed-off-by: Mark Rutland <mark.rutl...@arm.com>
Cc: Borislav Petkov <b...@suse.de>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@surriel.com>
Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
---
arch/x86/include/asm/fpu/internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/fpu/internal.h
b/arch/x86/include/asm/fpu/internal.h
index 4c95c365058a..ed3d85fa7c67 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -607,7 +607,7 @@ static inline void switch_fpu_finish(struct fpu *new_fpu)
* PKRU state is switched eagerly because it needs to be valid before we
* return to userland e.g. for a copy_to_user() operation.
*/
- if (current->mm) {
+ if (!is_kthread(current)) {
pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU);
if (pk)
pkru_val = pk->pkru;
--
2.11.0
