Commit 0d4ee88d authored by Paul Mackerras's avatar Paul Mackerras
Browse files

KVM: PPC: Book3S HV: Use new mutex to synchronize MMU setup 



Currently the HV KVM code uses kvm->lock in conjunction with a flag,
kvm->arch.mmu_ready, to synchronize MMU setup and hold off vcpu
execution until the MMU-related data structures are ready.  However,
this means that kvm->lock is being taken inside vcpu->mutex, which
is contrary to Documentation/virtual/kvm/locking.txt and results in
lockdep warnings.

To fix this, we add a new mutex, kvm->arch.mmu_setup_lock, which nests
inside the vcpu mutexes, and is taken in the places where kvm->lock
was taken that are related to MMU setup.

Additionally we take the new mutex in the vcpu creation code at the
point where we are creating a new vcore, in order to provide mutual
exclusion with kvmppc_update_lpcr() and ensure that an update to
kvm->arch.lpcr doesn't get missed, which could otherwise lead to a
stale vcore->lpcr value.

Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent c395fe1d

arch/powerpc/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -325,6 +325,7 @@ struct kvm_arch { 
#endif

	struct kvmppc_ops *kvm_ops;

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE

	struct mutex mmu_setup_lock;	/* nests inside vcpu mutexes */

	u64 l1_ptcr;

	int max_nested_lpid;

	struct kvm_nested_guest *nested_guests[KVM_MAX_NESTED_GUESTS];

arch/powerpc/kvm/book3s_64_mmu_hv.c

+18 −18
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ struct kvm_resize_hpt { 
	struct work_struct work;

	u32 order;



	/* These fields protected by kvm->lock */

	/* These fields protected by kvm->arch.mmu_setup_lock */



	/* Possible values and their usage:

	 *  <0     an error occurred during allocation,
@@ -73,7 +73,7 @@ struct kvm_resize_hpt { 
	int error;



	/* Private to the work thread, until error != -EBUSY,

	 * then protected by kvm->lock.

	 * then protected by kvm->arch.mmu_setup_lock.

	 */

	struct kvm_hpt_info hpt;

};
@@ -139,7 +139,7 @@ long kvmppc_alloc_reset_hpt(struct kvm *kvm, int order) 
	long err = -EBUSY;

	struct kvm_hpt_info info;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);

	if (kvm->arch.mmu_ready) {

		kvm->arch.mmu_ready = 0;

		/* order mmu_ready vs. vcpus_running */
@@ -183,7 +183,7 @@ out: 
		/* Ensure that each vcpu will flush its TLB on next entry. */

		cpumask_setall(&kvm->arch.need_tlb_flush);



	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);

	return err;

}
@@ -1447,7 +1447,7 @@ static void resize_hpt_pivot(struct kvm_resize_hpt *resize) 


static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize)

{

	if (WARN_ON(!mutex_is_locked(&kvm->lock)))

	if (WARN_ON(!mutex_is_locked(&kvm->arch.mmu_setup_lock)))

		return;



	if (!resize)
@@ -1474,14 +1474,14 @@ static void resize_hpt_prepare_work(struct work_struct *work) 
	if (WARN_ON(resize->error != -EBUSY))

		return;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);



	/* Request is still current? */

	if (kvm->arch.resize_hpt == resize) {

		/* We may request large allocations here:

		 * do not sleep with kvm->lock held for a while.

		 * do not sleep with kvm->arch.mmu_setup_lock held for a while.

		 */

		mutex_unlock(&kvm->lock);

		mutex_unlock(&kvm->arch.mmu_setup_lock);



		resize_hpt_debug(resize, "resize_hpt_prepare_work(): order = %d\n",

				 resize->order);
@@ -1494,9 +1494,9 @@ static void resize_hpt_prepare_work(struct work_struct *work) 
		if (WARN_ON(err == -EBUSY))

			err = -EINPROGRESS;



		mutex_lock(&kvm->lock);

		mutex_lock(&kvm->arch.mmu_setup_lock);

		/* It is possible that kvm->arch.resize_hpt != resize

		 * after we grab kvm->lock again.

		 * after we grab kvm->arch.mmu_setup_lock again.

		 */

	}
@@ -1505,7 +1505,7 @@ static void resize_hpt_prepare_work(struct work_struct *work) 
	if (kvm->arch.resize_hpt != resize)

		resize_hpt_release(kvm, resize);



	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);

}



long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm,
@@ -1522,7 +1522,7 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm, 
	if (shift && ((shift < 18) || (shift > 46)))

		return -EINVAL;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);



	resize = kvm->arch.resize_hpt;
@@ -1565,7 +1565,7 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm, 
	ret = 100; /* estimated time in ms */



out:

	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);

	return ret;

}
@@ -1588,7 +1588,7 @@ long kvm_vm_ioctl_resize_hpt_commit(struct kvm *kvm, 
	if (shift && ((shift < 18) || (shift > 46)))

		return -EINVAL;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);



	resize = kvm->arch.resize_hpt;
@@ -1625,7 +1625,7 @@ out: 
	smp_mb();

out_no_hpt:

	resize_hpt_release(kvm, resize);

	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);

	return ret;

}
@@ -1868,7 +1868,7 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf, 
		return -EINVAL;



	/* lock out vcpus from running while we're doing this */

	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);

	mmu_ready = kvm->arch.mmu_ready;

	if (mmu_ready) {

		kvm->arch.mmu_ready = 0;	/* temporarily */
@@ -1876,7 +1876,7 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf, 
		smp_mb();

		if (atomic_read(&kvm->arch.vcpus_running)) {

			kvm->arch.mmu_ready = 1;

			mutex_unlock(&kvm->lock);

			mutex_unlock(&kvm->arch.mmu_setup_lock);

			return -EBUSY;

		}

	}
@@ -1963,7 +1963,7 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf, 
	/* Order HPTE updates vs. mmu_ready */

	smp_wmb();

	kvm->arch.mmu_ready = mmu_ready;

	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);



	if (err)

		return err;

arch/powerpc/kvm/book3s_hv.c

+23 −8
Original line number Diff line number Diff line
@@ -2338,11 +2338,17 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_hv(struct kvm *kvm, 
			pr_devel("KVM: collision on id %u", id);

			vcore = NULL;

		} else if (!vcore) {

			/*

			 * Take mmu_setup_lock for mutual exclusion

			 * with kvmppc_update_lpcr().

			 */

			err = -ENOMEM;

			vcore = kvmppc_vcore_create(kvm,

					id & ~(kvm->arch.smt_mode - 1));

			mutex_lock(&kvm->arch.mmu_setup_lock);

			kvm->arch.vcores[core] = vcore;

			kvm->arch.online_vcores++;

			mutex_unlock(&kvm->arch.mmu_setup_lock);

		}

	}

	mutex_unlock(&kvm->lock);
@@ -3859,7 +3865,7 @@ static int kvmhv_setup_mmu(struct kvm_vcpu *vcpu) 
	int r = 0;

	struct kvm *kvm = vcpu->kvm;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);

	if (!kvm->arch.mmu_ready) {

		if (!kvm_is_radix(kvm))

			r = kvmppc_hv_setup_htab_rma(vcpu);
@@ -3869,7 +3875,7 @@ static int kvmhv_setup_mmu(struct kvm_vcpu *vcpu) 
			kvm->arch.mmu_ready = 1;

		}

	}

	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);

	return r;

}
@@ -4478,7 +4484,8 @@ static void kvmppc_core_commit_memory_region_hv(struct kvm *kvm, 


/*

 * Update LPCR values in kvm->arch and in vcores.

 * Caller must hold kvm->lock.

 * Caller must hold kvm->arch.mmu_setup_lock (for mutual exclusion

 * of kvm->arch.lpcr update).

 */

void kvmppc_update_lpcr(struct kvm *kvm, unsigned long lpcr, unsigned long mask)

{
@@ -4530,7 +4537,7 @@ void kvmppc_setup_partition_table(struct kvm *kvm) 


/*

 * Set up HPT (hashed page table) and RMA (real-mode area).

 * Must be called with kvm->lock held.

 * Must be called with kvm->arch.mmu_setup_lock held.

 */

static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)

{
@@ -4618,7 +4625,10 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu) 
	goto out_srcu;

}



/* Must be called with kvm->lock held and mmu_ready = 0 and no vcpus running */

/*

 * Must be called with kvm->arch.mmu_setup_lock held and

 * mmu_ready = 0 and no vcpus running.

 */

int kvmppc_switch_mmu_to_hpt(struct kvm *kvm)

{

	if (nesting_enabled(kvm))
@@ -4635,7 +4645,10 @@ int kvmppc_switch_mmu_to_hpt(struct kvm *kvm) 
	return 0;

}



/* Must be called with kvm->lock held and mmu_ready = 0 and no vcpus running */

/*

 * Must be called with kvm->arch.mmu_setup_lock held and

 * mmu_ready = 0 and no vcpus running.

 */

int kvmppc_switch_mmu_to_radix(struct kvm *kvm)

{

	int err;
@@ -4740,6 +4753,8 @@ static int kvmppc_core_init_vm_hv(struct kvm *kvm) 
	char buf[32];

	int ret;



	mutex_init(&kvm->arch.mmu_setup_lock);



	/* Allocate the guest's logical partition ID */



	lpid = kvmppc_alloc_lpid();
@@ -5265,7 +5280,7 @@ static int kvmhv_configure_mmu(struct kvm *kvm, struct kvm_ppc_mmuv3_cfg *cfg) 
	if (kvmhv_on_pseries() && !radix)

		return -EINVAL;



	mutex_lock(&kvm->lock);

	mutex_lock(&kvm->arch.mmu_setup_lock);

	if (radix != kvm_is_radix(kvm)) {

		if (kvm->arch.mmu_ready) {

			kvm->arch.mmu_ready = 0;
@@ -5293,7 +5308,7 @@ static int kvmhv_configure_mmu(struct kvm *kvm, struct kvm_ppc_mmuv3_cfg *cfg) 
	err = 0;



 out_unlock:

	mutex_unlock(&kvm->lock);

	mutex_unlock(&kvm->arch.mmu_setup_lock);

	return err;

}

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