Patch "x86/fpu: Don't set TIF_NEED_FPU_LOAD for PF_IO_WORKER threads" has been added to the 6.2-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    x86/fpu: Don't set TIF_NEED_FPU_LOAD for PF_IO_WORKER threads

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-fpu-don-t-set-tif_need_fpu_load-for-pf_io_worker.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 214e6c28a29204c5017f3c0ecf81665f1d1cce67
Author: Jens Axboe <axboe@xxxxxxxxx>
Date:   Tue Jan 24 08:23:20 2023 -0700

    x86/fpu: Don't set TIF_NEED_FPU_LOAD for PF_IO_WORKER threads
    
    [ Upstream commit cb3ea4b7671b7cfbac3ee609976b790aebd0bbda ]
    
    We don't set it on PF_KTHREAD threads as they never return to userspace,
    and PF_IO_WORKER threads are identical in that regard. As they keep
    running in the kernel until they die, skip setting the FPU flag on them.
    
    More of a cosmetic thing that was found while debugging and
    issue and pondering why the FPU flag is set on these threads.
    
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
    Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/560c844c-f128-555b-40c6-31baff27537f@xxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sched.h
index b2486b2cbc6e0..c2d6cd78ed0c2 100644
--- a/arch/x86/include/asm/fpu/sched.h
+++ b/arch/x86/include/asm/fpu/sched.h
@@ -39,7 +39,7 @@ extern void fpu_flush_thread(void);
 static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
 {
 	if (cpu_feature_enabled(X86_FEATURE_FPU) &&
-	    !(current->flags & PF_KTHREAD)) {
+	    !(current->flags & (PF_KTHREAD | PF_IO_WORKER))) {
 		save_fpregs_to_fpstate(old_fpu);
 		/*
 		 * The save operation preserved register state, so the
diff --git a/arch/x86/kernel/fpu/context.h b/arch/x86/kernel/fpu/context.h
index 958accf2ccf07..9fcfa5c4dad79 100644
--- a/arch/x86/kernel/fpu/context.h
+++ b/arch/x86/kernel/fpu/context.h
@@ -57,7 +57,7 @@ static inline void fpregs_restore_userregs(void)
 	struct fpu *fpu = &current->thread.fpu;
 	int cpu = smp_processor_id();
 
-	if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
+	if (WARN_ON_ONCE(current->flags & (PF_KTHREAD | PF_IO_WORKER)))
 		return;
 
 	if (!fpregs_state_valid(fpu, cpu)) {
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index dccce58201b7c..caf33486dc5ee 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -426,7 +426,7 @@ void kernel_fpu_begin_mask(unsigned int kfpu_mask)
 
 	this_cpu_write(in_kernel_fpu, true);
 
-	if (!(current->flags & PF_KTHREAD) &&
+	if (!(current->flags & (PF_KTHREAD | PF_IO_WORKER)) &&
 	    !test_thread_flag(TIF_NEED_FPU_LOAD)) {
 		set_thread_flag(TIF_NEED_FPU_LOAD);
 		save_fpregs_to_fpstate(&current->thread.fpu);