[PATCH AUTOSEL 5.1 52/70] KVM: PPC: Book3S HV: Use new mutex to synchronize MMU setup
Sasha Levin
sashal at kernel.org
Sat Jun 8 21:39:31 AEST 2019
From: Paul Mackerras <paulus at 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 at ozlabs.org>
Signed-off-by: Sasha Levin <sashal at 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;
}
--
2.20.1
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