[PATCH AUTOSEL 5.1 52/70] KVM: PPC: Book3S HV: Use new mutex to synchronize MMU setup

From: Paul Mackerras paulus@ozlabs.org

[ Upstream commit 0d4ee88d92884c661fcafd5576da243aa943dc24 ]

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: Paul Mackerras paulus@ozlabs.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/kvm_host.h | 1 + arch/powerpc/kvm/book3s_64_mmu_hv.c | 36 ++++++++++++++--------------- arch/powerpc/kvm/book3s_hv.c | 31 ++++++++++++++++++------- 3 files changed, 42 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index e6b5bb012ccb..8d3658275a34 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -317,6 +317,7 @@ 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]; diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index be7bc070eae5..c1ced22455f9 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -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; diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index b2b29d4f9842..4519c55ba19d 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -2257,11 +2257,17 @@ 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); @@ -3820,7 +3826,7 @@ 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); @@ -3830,7 +3836,7 @@ 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; }

@@ -4435,7 +4441,8 @@ 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) { @@ -4487,7 +4494,7 @@ 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) { @@ -4575,7 +4582,10 @@ 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)) @@ -4592,7 +4602,10 @@ 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; @@ -4697,6 +4710,8 @@ 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(); @@ -5222,7 +5237,7 @@ 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; @@ -5250,7 +5265,7 @@ 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; }