linux-kernel - [PATCH 3/4] KVM: kvm_main.c: Remove a global variable, hardware_enable

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Message-Id: <0836ee2f6c40091907092fc07fd50e64a499e6d1.1667369456.git.isaku.yamahata@intel.com>
Date:   Tue,  1 Nov 2022 23:24:10 -0700
From:   isaku.yamahata@...el.com
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com
Subject: [PATCH 3/4] KVM: kvm_main.c: Remove a global variable, hardware_enable_failed

From: Isaku Yamahata <isaku.yamahata@...el.com>

A global variable hardware_enable_failed in kvm_main.c is used only by
hardware_enable_all() and hardware_enable_nolock().  It doesn't have to be
a global variable.  Make it function local.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 virt/kvm/kvm_main.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1a21b21ba326..ac24fef2c818 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -105,7 +105,6 @@ LIST_HEAD(vm_list);
 
 static cpumask_t cpus_hardware_enabled = CPU_MASK_NONE;
 static int kvm_usage_count;
-static atomic_t hardware_enable_failed;
 
 static struct kmem_cache *kvm_vcpu_cache;
 
@@ -5007,30 +5006,36 @@ static struct miscdevice kvm_dev = {
 	&kvm_chardev_ops,
 };
 
-static void hardware_enable_nolock(void *junk)
+static int __hardware_enable_nolock(void)
 {
 	int cpu = raw_smp_processor_id();
 	int r;
 
-	if (cpumask_test_cpu(cpu, &cpus_hardware_enabled))
-		return;
-
-	cpumask_set_cpu(cpu, &cpus_hardware_enabled);
+	if (cpumask_test_and_set_cpu(cpu, &cpus_hardware_enabled))
+		return 0;
 
 	r = kvm_arch_hardware_enable();
 
 	if (r) {
 		cpumask_clear_cpu(cpu, &cpus_hardware_enabled);
-		atomic_inc(&hardware_enable_failed);
 		pr_info("kvm: enabling virtualization on CPU%d failed\n", cpu);
 	}
+	return r;
+}
+
+static void hardware_enable_nolock(void *arg)
+{
+	atomic_t *failed = arg;
+
+	if (__hardware_enable_nolock())
+		atomic_inc(failed);
 }
 
 static int kvm_starting_cpu(unsigned int cpu)
 {
 	raw_spin_lock(&kvm_count_lock);
 	if (kvm_usage_count)
-		hardware_enable_nolock(NULL);
+		(void)__hardware_enable_nolock();
 	raw_spin_unlock(&kvm_count_lock);
 	return 0;
 }
@@ -5072,16 +5077,16 @@ static void hardware_disable_all(void)
 
 static int hardware_enable_all(void)
 {
+	atomic_t failed = ATOMIC_INIT(0);
 	int r = 0;
 
 	raw_spin_lock(&kvm_count_lock);
 
 	kvm_usage_count++;
 	if (kvm_usage_count == 1) {
-		atomic_set(&hardware_enable_failed, 0);
-		on_each_cpu(hardware_enable_nolock, NULL, 1);
+		on_each_cpu(hardware_enable_nolock, &failed, 1);
 
-		if (atomic_read(&hardware_enable_failed)) {
+		if (atomic_read(&failed)) {
 			hardware_disable_all_nolock();
 			r = -EBUSY;
 		}
@@ -5702,7 +5707,7 @@ static void kvm_resume(void)
 {
 	if (kvm_usage_count) {
 		lockdep_assert_not_held(&kvm_count_lock);
-		hardware_enable_nolock(NULL);
+		(void)__hardware_enable_nolock();
 	}
 }
 
-- 
2.25.1