x86/xen: remove deprecated xen_nopvspin boot parameter

The xen_nopvspin boot parameter is deprecated since 2019. nopvspin
can be used instead.

Remove the xen_nopvspin boot parameter and replace the xen_pvspin
variable use cases with nopvspin.

This requires to move the nopvspin variable out of the .initdata
section, as it needs to be accessed for cpuhotplug, too.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <20240710110139.22300-1-jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -7439,11 +7439,6 @@
 			access functions when running as Xen PV guest. The
 			default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
 
-	xen_nopvspin	[X86,XEN,EARLY]
-			Disables the qspinlock slowpath using Xen PV optimizations.
-			This parameter is obsoleted by "nopvspin" parameter, which
-			has equivalent effect for XEN platform.
-
 	xen_nopv	[X86]
 			Disables the PV optimizations forcing the HVM guest to
 			run as generic HVM guest with no PV drivers.

arch/x86/xen/spinlock.c

@@ -18,7 +18,6 @@
 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
 static DEFINE_PER_CPU(char *, irq_name);
 static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
-static bool xen_pvspin = true;
 
 static void xen_qlock_kick(int cpu)
 {
@@ -68,7 +67,7 @@ void xen_init_lock_cpu(int cpu)
 	int irq;
 	char *name;
 
-	if (!xen_pvspin)
+	if (nopvspin)
 		return;
 
 	WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
@@ -95,7 +94,7 @@ void xen_uninit_lock_cpu(int cpu)
 {
 	int irq;
 
-	if (!xen_pvspin)
+	if (nopvspin)
 		return;
 
 	kfree(per_cpu(irq_name, cpu));
@@ -125,10 +124,10 @@ PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
 void __init xen_init_spinlocks(void)
 {
 	/*  Don't need to use pvqspinlock code if there is only 1 vCPU. */
-	if (num_possible_cpus() == 1 || nopvspin)
-		xen_pvspin = false;
+	if (num_possible_cpus() == 1)
+		nopvspin = true;
 
-	if (!xen_pvspin) {
+	if (nopvspin) {
 		printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
 		static_branch_disable(&virt_spin_lock_key);
 		return;
@@ -143,12 +142,3 @@ void __init xen_init_spinlocks(void)
 	pv_ops.lock.kick = xen_qlock_kick;
 	pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
 }
-
-static __init int xen_parse_nopvspin(char *arg)
-{
-	pr_notice("\"xen_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
-	xen_pvspin = false;
-	return 0;
-}
-early_param("xen_nopvspin", xen_parse_nopvspin);
-

kernel/locking/qspinlock.c

@@ -583,7 +583,7 @@ EXPORT_SYMBOL(queued_spin_lock_slowpath);
 #include "qspinlock_paravirt.h"
 #include "qspinlock.c"
 
-bool nopvspin __initdata;
+bool nopvspin;
 static __init int parse_nopvspin(char *arg)
 {
 	nopvspin = true;