[tip: x86/merge] x86/fpu: Clarify FPU context cacheline alignment

[tip-bot2 for Ingo Molnar]

The following commit has been merged into the x86/merge branch of tip:

Commit-ID:     e3a52b67f54aa36ab21265eeea016460b5fe1c46
Gitweb:        https://git.kernel.org/tip/e3a52b67f54aa36ab21265eeea016460b5fe1c46
Author:        Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate:    Thu, 10 Apr 2025 12:52:16 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Mon, 14 Apr 2025 08:18:29 +02:00

x86/fpu: Clarify FPU context cacheline alignment

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/Z_ejggklB5-IWB5W@xxxxxxxxx
---
 arch/x86/kernel/fpu/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index d0a45f6..3a19877 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -607,7 +607,8 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
 	 * We allocate the new FPU structure right after the end of the task struct.
 	 * task allocation size already took this into account.
 	 *
-	 * This is safe because task_struct size is a multiple of cacheline size.
+	 * This is safe because task_struct size is a multiple of cacheline size,
+	 * thus x86_task_fpu() will always be cacheline aligned as well.
 	 */
 	struct fpu *dst_fpu = (void *)dst + sizeof(*dst);