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KVM: arm64: Use config_lock to protect data ordered against KVM_RUN 

commit 4bba7f7def upstream.

There are various bits of VM-scoped data that can only be configured
before the first call to KVM_RUN, such as the hypercall bitmaps and
the PMU. As these fields are protected by the kvm->lock and accessed
while holding vcpu->mutex, this is yet another example of lock
inversion.

Change out the kvm->lock for kvm->arch.config_lock in all of these
instances. Opportunistically simplify the locking mechanics of the
PMU configuration by holding the config_lock for the entirety of
kvm_arm_pmu_v3_set_attr().

Note that this also addresses a couple of bugs. There is an unguarded
read of the PMU version in KVM_ARM_VCPU_PMU_V3_FILTER which could race
with KVM_ARM_VCPU_PMU_V3_SET_PMU. Additionally, until now writes to the
per-vCPU vPMU irq were not serialized VM-wide, meaning concurrent calls
to KVM_ARM_VCPU_PMU_V3_IRQ could lead to a false positive in
pmu_irq_is_valid().

Cc: stable@vger.kernel.org
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230327164747.2466958-4-oliver.upton@linux.dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Oliver Upton 2023-03-27 16:47:46 +00:00 committed by Greg Kroah-Hartman
parent 6c9d3f2a5e
commit 2b57af7bb9
4 changed files with 12 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/arm64/kvm/arm.c
View File

@ -616,9 +616,9 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
if (kvm_vm_is_protected(kvm))
kvm_call_hyp_nvhe(__pkvm_vcpu_init_traps, vcpu);
mutex_lock(&kvm->lock);
mutex_lock(&kvm->arch.config_lock);
set_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &kvm->arch.flags);
mutex_unlock(&kvm->lock);
mutex_unlock(&kvm->arch.config_lock);
return ret;
}

2
arch/arm64/kvm/guest.c
View File

@ -951,7 +951,9 @@ int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu,
switch (attr->group) {
case KVM_ARM_VCPU_PMU_V3_CTRL:
mutex_lock(&vcpu->kvm->arch.config_lock);
ret = kvm_arm_pmu_v3_set_attr(vcpu, attr);
mutex_unlock(&vcpu->kvm->arch.config_lock);
break;
case KVM_ARM_VCPU_TIMER_CTRL:
ret = kvm_arm_timer_set_attr(vcpu, attr);

4
arch/arm64/kvm/hypercalls.c
View File

@ -377,7 +377,7 @@ static int kvm_arm_set_fw_reg_bmap(struct kvm_vcpu *vcpu, u64 reg_id, u64 val)
if (val & ~fw_reg_features)
return -EINVAL;
mutex_lock(&kvm->lock);
mutex_lock(&kvm->arch.config_lock);
if (test_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &kvm->arch.flags) &&
val != *fw_reg_bmap) {
@ -387,7 +387,7 @@ static int kvm_arm_set_fw_reg_bmap(struct kvm_vcpu *vcpu, u64 reg_id, u64 val)
WRITE_ONCE(*fw_reg_bmap, val);
out:
mutex_unlock(&kvm->lock);
mutex_unlock(&kvm->arch.config_lock);
return ret;
}

23
arch/arm64/kvm/pmu-emul.c
View File

@ -850,7 +850,7 @@ static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
struct arm_pmu *arm_pmu;
int ret = -ENXIO;
mutex_lock(&kvm->lock);
lockdep_assert_held(&kvm->arch.config_lock);
mutex_lock(&arm_pmus_lock);
list_for_each_entry(entry, &arm_pmus, entry) {
@ -870,7 +870,6 @@ static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
}
mutex_unlock(&arm_pmus_lock);
mutex_unlock(&kvm->lock);
return ret;
}
@ -878,22 +877,20 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
struct kvm *kvm = vcpu->kvm;
lockdep_assert_held(&kvm->arch.config_lock);
if (!kvm_vcpu_has_pmu(vcpu))
return -ENODEV;
if (vcpu->arch.pmu.created)
return -EBUSY;
mutex_lock(&kvm->lock);
if (!kvm->arch.arm_pmu) {
/* No PMU set, get the default one */
kvm->arch.arm_pmu = kvm_pmu_probe_armpmu();
if (!kvm->arch.arm_pmu) {
mutex_unlock(&kvm->lock);
if (!kvm->arch.arm_pmu)
return -ENODEV;
}
}
mutex_unlock(&kvm->lock);
switch (attr->attr) {
case KVM_ARM_VCPU_PMU_V3_IRQ: {
@ -937,19 +934,13 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
filter.action != KVM_PMU_EVENT_DENY))
return -EINVAL;
mutex_lock(&kvm->lock);
if (test_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &kvm->arch.flags)) {
mutex_unlock(&kvm->lock);
if (test_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &kvm->arch.flags))
return -EBUSY;
}
if (!kvm->arch.pmu_filter) {
kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL_ACCOUNT);
if (!kvm->arch.pmu_filter) {
mutex_unlock(&kvm->lock);
if (!kvm->arch.pmu_filter)
return -ENOMEM;
}
/*
* The default depends on the first applied filter.
@ -968,8 +959,6 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
else
bitmap_clear(kvm->arch.pmu_filter, filter.base_event, filter.nevents);
mutex_unlock(&kvm->lock);
return 0;
}
case KVM_ARM_VCPU_PMU_V3_SET_PMU: {