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Commit c6170b81 authored by Junaid Shahid's avatar Junaid Shahid Committed by Greg Kroah-Hartman
Browse files

kvm: Convert kvm_lock to a mutex 



commit 0d9ce162cf46c99628cc5da9510b959c7976735b upstream.

It doesn't seem as if there is any particular need for kvm_lock to be a
spinlock, so convert the lock to a mutex so that sleepable functions (in
particular cond_resched()) can be called while holding it.

Signed-off-by: default avatarJunaid Shahid <junaids@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 4.9:
 - Drop changes in kvm_hyperv_tsc_notifier(), vm_stat_clear(),
   vcpu_stat_clear(), kvm_uevent_notify_change()
 - Adjust context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 61524f1b

Documentation/virtual/kvm/locking.txt

+3 −3
Original line number Diff line number Diff line
@@ -13,8 +13,8 @@ The acquisition orders for mutexes are as follows: 
- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring

  them together is quite rare.



For spinlocks, kvm_lock is taken outside kvm->mmu_lock.  Everything

else is a leaf: no other lock is taken inside the critical sections.

Everything else is a leaf: no other lock is taken inside the critical

sections.



2: Exception

------------
@@ -142,7 +142,7 @@ See the comments in spte_has_volatile_bits() and mmu_spte_update(). 
------------



Name:		kvm_lock

Type:		spinlock_t

Type:		mutex

Arch:		any

Protects:	- vm_list

arch/s390/kvm/kvm-s390.c

+2 −2
Original line number Diff line number Diff line
@@ -1422,13 +1422,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 
	kvm->arch.sca = (struct bsca_block *) get_zeroed_page(alloc_flags);

	if (!kvm->arch.sca)

		goto out_err;

	spin_lock(&kvm_lock);

	mutex_lock(&kvm_lock);

	sca_offset += 16;

	if (sca_offset + sizeof(struct bsca_block) > PAGE_SIZE)

		sca_offset = 0;

	kvm->arch.sca = (struct bsca_block *)

			((char *) kvm->arch.sca + sca_offset);

	spin_unlock(&kvm_lock);

	mutex_unlock(&kvm_lock);



	sprintf(debug_name, "kvm-%u", current->pid);

arch/x86/kvm/mmu.c

+2 −2
Original line number Diff line number Diff line
@@ -4979,7 +4979,7 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) 
	int nr_to_scan = sc->nr_to_scan;

	unsigned long freed = 0;



	spin_lock(&kvm_lock);

	mutex_lock(&kvm_lock);



	list_for_each_entry(kvm, &vm_list, vm_list) {

		int idx;
@@ -5029,7 +5029,7 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) 
		break;

	}



	spin_unlock(&kvm_lock);

	mutex_unlock(&kvm_lock);

	return freed;

}

arch/x86/kvm/x86.c

+5 −5
Original line number Diff line number Diff line
@@ -5978,17 +5978,17 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va 


	smp_call_function_single(freq->cpu, tsc_khz_changed, freq, 1);



	spin_lock(&kvm_lock);

	mutex_lock(&kvm_lock);

	list_for_each_entry(kvm, &vm_list, vm_list) {

		kvm_for_each_vcpu(i, vcpu, kvm) {

			if (vcpu->cpu != freq->cpu)

				continue;

			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);

			if (vcpu->cpu != smp_processor_id())

			if (vcpu->cpu != raw_smp_processor_id())

				send_ipi = 1;

		}

	}

	spin_unlock(&kvm_lock);

	mutex_unlock(&kvm_lock);



	if (freq->old < freq->new && send_ipi) {

		/*
@@ -6126,12 +6126,12 @@ static void pvclock_gtod_update_fn(struct work_struct *work) 
	struct kvm_vcpu *vcpu;

	int i;



	spin_lock(&kvm_lock);

	mutex_lock(&kvm_lock);

	list_for_each_entry(kvm, &vm_list, vm_list)

		kvm_for_each_vcpu(i, vcpu, kvm)

			kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);

	atomic_set(&kvm_guest_has_master_clock, 0);

	spin_unlock(&kvm_lock);

	mutex_unlock(&kvm_lock);

}



static DECLARE_WORK(pvclock_gtod_work, pvclock_gtod_update_fn);

include/linux/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) 


extern struct kmem_cache *kvm_vcpu_cache;



extern spinlock_t kvm_lock;

extern struct mutex kvm_lock;

extern struct list_head vm_list;



struct kvm_io_range {