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KVM: x86: use dynamic percpu allocations for shared msrs area

PATCH Marcelo Tosatti 4 participants 4 messages Jan 3, 2013 – Feb 1, 2013

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x86 KVM KVM x86
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Marcelo Tosatti

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#0 lore raw

Andy, Mike, can you confirm whether this fixes the percpu allocation failures when loading kvm.ko? TIA

----

Use dynamic percpu allocations for the shared msrs structure, to avoid using the limited reserved percpu space.

Signed-off-by Marcelo Tosatti <[email protected]>
arch/x86/kvm/x86.c +18 -6
index 1c9c834..5229a67 100644
@@ -120,7 +120,7 @@ struct kvm_shared_msrs {
 };
 
 static struct kvm_shared_msrs_global __read_mostly shared_msrs_global;
-static DEFINE_PER_CPU(struct kvm_shared_msrs, shared_msrs);
+static struct kvm_shared_msrs __percpu *shared_msrs;
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
 	{ "pf_fixed", VCPU_STAT(pf_fixed) },

@@ -191,10 +191,10 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
 
 static void shared_msr_update(unsigned slot, u32 msr)
 {
-	struct kvm_shared_msrs *smsr;
 	u64 value;
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
-	smsr = &__get_cpu_var(shared_msrs);
 	/* only read, and nobody should modify it at this time,
 	 * so don't need lock */
 	if (slot >= shared_msrs_global.nr) {

@@ -226,7 +226,8 @@ static void kvm_shared_msr_cpu_online(void)
 
 void kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
 {
-	struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
 	if (((value ^ smsr->values[slot].curr) & mask) == 0)
 		return;

@@ -242,7 +243,8 @@ EXPORT_SYMBOL_GPL(kvm_set_shared_msr);
 
 static void drop_user_return_notifiers(void *ignore)
 {
-	struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
 	if (smsr->registered)
 		kvm_on_user_return(&smsr->urn);

@@ -5233,9 +5235,16 @@ int kvm_arch_init(void *opaque)
 		goto out;
 	}
 
+	r = -ENOMEM;
+	shared_msrs = alloc_percpu(struct kvm_shared_msrs);
+	if (!shared_msrs) {
+		printk(KERN_ERR "kvm: failed to allocate percpu kvm_shared_msrs\n");
+		goto out;
+	}
+
 	r = kvm_mmu_module_init();
 	if (r)
-		goto out;
+		goto out_free_percpu;
 
 	kvm_set_mmio_spte_mask();
 	kvm_init_msr_list();

@@ -5258,6 +5267,8 @@ int kvm_arch_init(void *opaque)
 
 	return 0;
 
+out_free_percpu:
+	free_percpu(shared_msrs);
 out:
 	return r;
 }

@@ -5275,6 +5286,7 @@ void kvm_arch_exit(void)
 #endif
 	kvm_x86_ops = NULL;
 	kvm_mmu_module_exit();
+	free_percpu(shared_msrs);
 }
 
 int kvm_emulate_halt(struct kvm_vcpu *vcpu)
#1 lore raw
Quoted 2 lines · Marcelo Tosatti

Andy, Mike, can you confirm whether this fixes the percpu allocation failures when loading kvm.ko? TIA

monteverdi:~/:[1]# dmesg|grep PERCPU
[    0.000000] PERCPU: Embedded 27 pages/cpu @ffff88047f800000 s80704 r8192 d21696 u262144
monteverdi:~/:[0]# lsmod|grep kvm
kvm_intel             132688  0 
kvm                   423692  1 kvm_intel
monteverdi:~/:[0]# uname -r
3.6.0-bisect

Yup, kvm loaded itself, no gripeage.

Quoted 88 lines

----

Use dynamic percpu allocations for the shared msrs structure, to avoid using the limited reserved percpu space.

Signed-off-by Marcelo Tosatti <[email protected]>
arch/x86/kvm/x86.c +18 -6
index 1c9c834..5229a67 100644
@@ -120,7 +120,7 @@ struct kvm_shared_msrs {
 };
 
 static struct kvm_shared_msrs_global __read_mostly shared_msrs_global;
-static DEFINE_PER_CPU(struct kvm_shared_msrs, shared_msrs);
+static struct kvm_shared_msrs __percpu *shared_msrs;
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
 	{ "pf_fixed", VCPU_STAT(pf_fixed) },

@@ -191,10 +191,10 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
 
 static void shared_msr_update(unsigned slot, u32 msr)
 {
-	struct kvm_shared_msrs *smsr;
 	u64 value;
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
-	smsr = &__get_cpu_var(shared_msrs);
 	/* only read, and nobody should modify it at this time,
 	 * so don't need lock */
 	if (slot >= shared_msrs_global.nr) {

@@ -226,7 +226,8 @@ static void kvm_shared_msr_cpu_online(void)
 
 void kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
 {
-	struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
 	if (((value ^ smsr->values[slot].curr) & mask) == 0)
 		return;

@@ -242,7 +243,8 @@ EXPORT_SYMBOL_GPL(kvm_set_shared_msr);
 
 static void drop_user_return_notifiers(void *ignore)
 {
-	struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
 	if (smsr->registered)
 		kvm_on_user_return(&smsr->urn);

@@ -5233,9 +5235,16 @@ int kvm_arch_init(void *opaque)
 		goto out;
 	}
 
+	r = -ENOMEM;
+	shared_msrs = alloc_percpu(struct kvm_shared_msrs);
+	if (!shared_msrs) {
+		printk(KERN_ERR "kvm: failed to allocate percpu kvm_shared_msrs\n");
+		goto out;
+	}
+
 	r = kvm_mmu_module_init();
 	if (r)
-		goto out;
+		goto out_free_percpu;
 
 	kvm_set_mmio_spte_mask();
 	kvm_init_msr_list();

@@ -5258,6 +5267,8 @@ int kvm_arch_init(void *opaque)
 
 	return 0;
 
+out_free_percpu:
+	free_percpu(shared_msrs);
 out:
 	return r;
 }

@@ -5275,6 +5286,7 @@ void kvm_arch_exit(void)
 #endif
 	kvm_x86_ops = NULL;
 	kvm_mmu_module_exit();
+	free_percpu(shared_msrs);
 }
 
 int kvm_emulate_halt(struct kvm_vcpu *vcpu)
Reviewed-by
#2 lore raw
In reply to Marcelo Tosatti
Quoted 11 lines · Marcelo Tosatti

Andy, Mike, can you confirm whether this fixes the percpu allocation failures when loading kvm.ko? TIA

----

Use dynamic percpu allocations for the shared msrs structure, to avoid using the limited reserved percpu space.

Signed-off-by Marcelo Tosatti <[email protected]>
Reviewed-by Gleb Natapov <[email protected]>
Quoted 82 lines
arch/x86/kvm/x86.c +18 -7
index 1c9c834..5229a67 100644
@@ -120,7 +120,7 @@ struct kvm_shared_msrs {
 };
 
 static struct kvm_shared_msrs_global __read_mostly shared_msrs_global;
-static DEFINE_PER_CPU(struct kvm_shared_msrs, shared_msrs);
+static struct kvm_shared_msrs __percpu *shared_msrs;
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
 	{ "pf_fixed", VCPU_STAT(pf_fixed) },

@@ -191,10 +191,10 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
 
 static void shared_msr_update(unsigned slot, u32 msr)
 {
-	struct kvm_shared_msrs *smsr;
 	u64 value;
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
-	smsr = &__get_cpu_var(shared_msrs);
 	/* only read, and nobody should modify it at this time,
 	 * so don't need lock */
 	if (slot >= shared_msrs_global.nr) {

@@ -226,7 +226,8 @@ static void kvm_shared_msr_cpu_online(void)
 
 void kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
 {
-	struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
 	if (((value ^ smsr->values[slot].curr) & mask) == 0)
 		return;

@@ -242,7 +243,8 @@ EXPORT_SYMBOL_GPL(kvm_set_shared_msr);
 
 static void drop_user_return_notifiers(void *ignore)
 {
-	struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
+	unsigned int cpu = smp_processor_id();
+	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
 
 	if (smsr->registered)
 		kvm_on_user_return(&smsr->urn);

@@ -5233,9 +5235,16 @@ int kvm_arch_init(void *opaque)
 		goto out;
 	}
 
+	r = -ENOMEM;
+	shared_msrs = alloc_percpu(struct kvm_shared_msrs);
+	if (!shared_msrs) {
+		printk(KERN_ERR "kvm: failed to allocate percpu kvm_shared_msrs\n");
+		goto out;
+	}
+
 	r = kvm_mmu_module_init();
 	if (r)
-		goto out;
+		goto out_free_percpu;
 
 	kvm_set_mmio_spte_mask();
 	kvm_init_msr_list();

@@ -5258,6 +5267,8 @@ int kvm_arch_init(void *opaque)
 
 	return 0;
 
+out_free_percpu:
+	free_percpu(shared_msrs);
 out:
 	return r;
 }

@@ -5275,6 +5286,7 @@ void kvm_arch_exit(void)
 #endif
 	kvm_x86_ops = NULL;
 	kvm_mmu_module_exit();
+	free_percpu(shared_msrs);
 }
 
 int kvm_emulate_halt(struct kvm_vcpu *vcpu)
--
Quoted 3 lines

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--
Gleb.

#3 lore raw
In reply to Marcelo Tosatti
Quoted 10 lines · Marcelo Tosatti

Andy, Mike, can you confirm whether this fixes the percpu allocation failures when loading kvm.ko? TIA

----

Use dynamic percpu allocations for the shared msrs structure, to avoid using the limited reserved percpu space.

Signed-off-by Marcelo Tosatti <[email protected]>

Sorry for the amazingly long delay. What kernel does this apply to?

--Andy