pokestress.patch

commit baffbe58c26ce8e0105f54916ae548a1e1c283a0
Author: Omar Sandoval <osandov@fb.com>
Date:   Mon Oct 27 15:51:10 2025 -0700

    Test patch to stress smp_text_poke_int3_handler()
    
    Build this with the following config:
    
    CONFIG_SMP=y
    CONFIG_MODULES=n
    CONFIG_CC_OPTIMIZE_FOR_SIZE=y
    CONFIG_BLK_DEV_INITRD=y
    CONFIG_RTC_CLASS=y
    CONFIG_RTC_DRV_CMOS=y
    CONFIG_SERIAL_8250=y
    CONFIG_SERIAL_8250_CONSOLE=y
    CONFIG_HYPERVISOR_GUEST=y
    CONFIG_KVM_GUEST=y
    CONFIG_PARAVIRT=y
    CONFIG_PARAVIRT_SPINLOCKS=y
    CONFIG_JUMP_LABEL=y

diff --git a/kernel/Makefile b/kernel/Makefile
index df3dd8291bb6..ac9f8a79acf7 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -205,3 +205,5 @@ $(obj)/kheaders.md5: $(obj)/kheaders-srclist FORCE
 	$(call filechk,kheaders_md5sum)
 
 clean-files := kheaders.md5 kheaders-srclist kheaders-objlist
+
+obj-y += pokestress.o
diff --git a/kernel/pokestress.c b/kernel/pokestress.c
new file mode 100644
index 000000000000..a245f534e4ad
--- /dev/null
+++ b/kernel/pokestress.c
@@ -0,0 +1,93 @@
+#include <linux/delay.h>
+#include <linux/jump_label.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/pgtable.h>
+#include <linux/slab.h>
+#include <asm/cpu_entry_area.h>
+
+DEFINE_STATIC_KEY_FALSE(my_key);
+
+static struct task_struct *toggle_thread;
+static struct task_struct **branch_threads;
+static unsigned int num_branch_threads;
+
+static int toggle_func(void *arg)
+{
+	while (!kthread_should_stop()) {
+		static_branch_enable(&my_key);
+		static_branch_disable(&my_key);
+		cond_resched();
+	}
+	return 0;
+}
+
+static int branch_func(void *arg)
+{
+	while (!kthread_should_stop()) {
+		if (static_branch_unlikely(&my_key))
+			asm volatile(".rept 4096\nnop\n.endr\n");
+		else
+			asm volatile(".rept 2048\n.nops 2\n.endr\n");
+		cond_resched();
+	}
+	return 0;
+}
+
+static void pokestress_exit(void)
+{
+	unsigned int i;
+
+	if (branch_threads) {
+		for (i = 0; i < num_branch_threads; i++) {
+			if (branch_threads[i])
+				kthread_stop(branch_threads[i]);
+		}
+		kfree(branch_threads);
+	}
+	if (toggle_thread)
+		kthread_stop(toggle_thread);
+}
+
+static int __init pokestress_init(void)
+{
+	struct task_struct *thread;
+	unsigned int i;
+
+	for_each_online_cpu(i) {
+		phys_addr_t gpa;
+
+		gpa = slow_virt_to_phys(&get_cpu_entry_area(i)->tss);
+		pr_crit("GPA=%pap\n", &gpa);
+	}
+
+	thread = kthread_run(toggle_func, NULL, "toggle");
+	if (IS_ERR(thread))
+		return PTR_ERR(thread);
+	toggle_thread = thread;
+
+	num_branch_threads = max(num_online_cpus() - 1, 1U);
+	branch_threads = kcalloc(num_branch_threads, sizeof(*branch_threads),
+				 GFP_KERNEL);
+	if (!branch_threads) {
+		pokestress_exit();
+		return -ENOMEM;
+	}
+	for (i = 0; i < num_branch_threads; i++) {
+		thread = kthread_run(branch_func, NULL, "branch%u", i);
+		if (IS_ERR(thread)) {
+			pokestress_exit();
+			return PTR_ERR(thread);
+		}
+		branch_threads[i] = thread;
+	}
+
+	pr_crit("POKESTRESS RUNNING\n");
+
+	return 0;
+}
+
+module_init(pokestress_init);
+module_exit(pokestress_exit);
+
+MODULE_LICENSE("GPL");