lkml.org 
[lkml]   [2017]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH] KVM: nVMX: do not pin the VMCS12
From
Date
On 27/07/2017 19:20, David Matlack wrote:
>> + kvm_vcpu_write_guest_page(&vmx->vcpu,
>> + vmx->nested.current_vmptr >> PAGE_SHIFT,
>> + vmx->nested.cached_vmcs12, 0, VMCS12_SIZE);
> Have you hit any "suspicious RCU usage" error messages during VM
> teardown with this patch? We did when we replaced memcpy with
> kvm_write_guest a while back. IIRC it was due to kvm->srcu not being
> held in one of the teardown paths. kvm_write_guest() expects it to be
> held in order to access memslots.
>
> We fixed this by skipping the VMCS12 flush during VMXOFF. I'll send
> that patch along with a few other nVMX dirty tracking related patches
> I've been meaning to get upstreamed.

Oh, right. I had this other (untested) patch in the queue after
Christian recently annotated everything with RCU checks:

Paolo

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 890b706d1943..07e3b02a1be3 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -477,7 +477,8 @@ struct kvm {
static inline struct kvm_io_bus *kvm_get_bus(struct kvm *kvm, enum kvm_bus idx)
{
return srcu_dereference_check(kvm->buses[idx], &kvm->srcu,
- lockdep_is_held(&kvm->slots_lock));
+ lockdep_is_held(&kvm->slots_lock) ||
+ !refcount_read(&kvm->users_count));
}

static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
@@ -570,7 +571,8 @@ void kvm_put_kvm(struct kvm *kvm);
static inline struct kvm_memslots *__kvm_memslots(struct kvm *kvm, int as_id)
{
return srcu_dereference_check(kvm->memslots[as_id], &kvm->srcu,
- lockdep_is_held(&kvm->slots_lock));
+ lockdep_is_held(&kvm->slots_lock) ||
+ !refcount_read(&kvm->users_count));
}

static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f3f74271f1a9..6a21c98b22bf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -655,7 +655,6 @@ static struct kvm *kvm_create_vm(unsigned long type)
mutex_init(&kvm->lock);
mutex_init(&kvm->irq_lock);
mutex_init(&kvm->slots_lock);
- refcount_set(&kvm->users_count, 1);
INIT_LIST_HEAD(&kvm->devices);

r = kvm_arch_init_vm(kvm, type);
@@ -701,6 +700,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
if (r)
goto out_err;

+ refcount_set(&kvm->users_count, 1);
spin_lock(&kvm_lock);
list_add(&kvm->vm_list, &vm_list);
spin_unlock(&kvm_lock);
@@ -717,10 +717,9 @@ static struct kvm *kvm_create_vm(unsigned long type)
hardware_disable_all();
out_err_no_disable:
for (i = 0; i < KVM_NR_BUSES; i++)
- kfree(rcu_access_pointer(kvm->buses[i]));
+ kfree(kvm_get_bus(kvm, i));
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
- kvm_free_memslots(kvm,
- rcu_dereference_protected(kvm->memslots[i], 1));
+ kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
kvm_arch_free_vm(kvm);
mmdrop(current->mm);
return ERR_PTR(r);
@@ -754,9 +754,8 @@ static void kvm_destroy_vm(struct kvm *kvm)
spin_unlock(&kvm_lock);
kvm_free_irq_routing(kvm);
for (i = 0; i < KVM_NR_BUSES; i++) {
- struct kvm_io_bus *bus;
+ struct kvm_io_bus *bus = kvm_get_bus(kvm, i);

- bus = rcu_dereference_protected(kvm->buses[i], 1);
if (bus)
kvm_io_bus_destroy(bus);
kvm->buses[i] = NULL;
@@ -770,8 +769,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
kvm_arch_destroy_vm(kvm);
kvm_destroy_devices(kvm);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
- kvm_free_memslots(kvm,
- rcu_dereference_protected(kvm->memslots[i], 1));
+ kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
cleanup_srcu_struct(&kvm->irq_srcu);
cleanup_srcu_struct(&kvm->srcu);
kvm_arch_free_vm(kvm);
\
 
 \ /
  Last update: 2017-07-28 08:58    [W:0.064 / U:9.540 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site