Re: [PATCH] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

2012-03-06 Thread Avi Kivity 
On 03/06/2012 07:30 AM, Michael Ellerman wrote:
 On Mon, 2012-03-05 at 14:29 +0200, Avi Kivity wrote:
  If some vcpus are created before KVM_CREATE_IRQCHIP, then
  irqchip_in_kernel() and vcpu-arch.apic will be inconsistent, leading
  to potential NULL pointer dereferences.
  
  Fix by:
  - ensuring that no vcpus are installed when KVM_CREATE_IRQCHIP is called
  - ensuring that a vcpu has an apic if it is installed after 
  KVM_CREATE_IRQCHIP
  
  This is somewhat long winded because vcpu-arch.apic is created without
  kvm-lock held.

 Hi Avi,

 Thanks for following up on this. This looks OK to me.

 I wonder if we will end up needing to add other sanity tests at the same
 point, ie. when we install the vcpu, in which case we might need a
 generic sanity hook. But better to keep it specific until we need
 something generalised.

Right, ARM will also have the same problem (with/without GIC).

 When we do irqchip-in-kernel on powerpc we'll need to rework the #ifdef
 in kvm_host.h, because we don't want CONFIG_KVM_APIC_ARCHITECTURE, but
 we will need our own kvm_vcpu_compatible(). But again we'll do that at
 the time.


-- 
error compiling committee.c: too many arguments to function

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[PATCH] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

2012-03-05 Thread Avi Kivity 
If some vcpus are created before KVM_CREATE_IRQCHIP, then
irqchip_in_kernel() and vcpu-arch.apic will be inconsistent, leading
to potential NULL pointer dereferences.

Fix by:
- ensuring that no vcpus are installed when KVM_CREATE_IRQCHIP is called
- ensuring that a vcpu has an apic if it is installed after KVM_CREATE_IRQCHIP

This is somewhat long winded because vcpu-arch.apic is created without
kvm-lock held.

Based on earlier patch by Michael Ellerman.

Signed-off-by: Michael Ellerman mich...@ellerman.id.au
Signed-off-by: Avi Kivity a...@redhat.com
---
 arch/ia64/kvm/kvm-ia64.c |5 +
 arch/x86/kvm/x86.c   |8 
 include/linux/kvm_host.h |7 +++
 virt/kvm/kvm_main.c  |4 
 4 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index d8ddbba..f5104b7 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1172,6 +1172,11 @@ static enum hrtimer_restart hlt_timer_fn(struct hrtimer 
*data)
 
 #define PALE_RESET_ENTRY0x8000ffb0UL
 
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
+{
+   return irqchip_in_kernel(vcpu-kcm) == (vcpu-arch.apic != NULL);
+}
+
 int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 {
struct kvm_vcpu *v;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3ee008f..be9594a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3199,6 +3199,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = -EEXIST;
if (kvm-arch.vpic)
goto create_irqchip_unlock;
+   r = -EINVAL;
+   if (atomic_read(kvm-online_vcpus))
+   goto create_irqchip_unlock;
r = -ENOMEM;
vpic = kvm_create_pic(kvm);
if (vpic) {
@@ -6107,6 +6110,11 @@ void kvm_arch_check_processor_compat(void *rtn)
kvm_x86_ops-check_processor_compatibility(rtn);
 }
 
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
+{
+   return irqchip_in_kernel(vcpu-kvm) == (vcpu-arch.apic != NULL);
+}
+
 int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 {
struct page *page;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 355e445..759fa26 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -805,6 +805,13 @@ static inline bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
 {
return vcpu-kvm-bsp_vcpu_id == vcpu-vcpu_id;
 }
+
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
+
+#else
+
+static bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu) { return true; }
+
 #endif
 
 #ifdef __KVM_HAVE_DEVICE_ASSIGNMENT
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e4431ad..94e148e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1651,6 +1651,10 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 
id)
goto vcpu_destroy;
 
mutex_lock(kvm-lock);
+   if (!kvm_vcpu_compatible(vcpu)) {
+   r = -EINVAL;
+   goto unlock_vcpu_destroy;
+   }
if (atomic_read(kvm-online_vcpus) == KVM_MAX_VCPUS) {
r = -EINVAL;
goto unlock_vcpu_destroy;
-- 
1.7.9

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Re: [PATCH] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

2012-03-05 Thread Michael Ellerman 
On Mon, 2012-03-05 at 14:29 +0200, Avi Kivity wrote:
 If some vcpus are created before KVM_CREATE_IRQCHIP, then
 irqchip_in_kernel() and vcpu-arch.apic will be inconsistent, leading
 to potential NULL pointer dereferences.
 
 Fix by:
 - ensuring that no vcpus are installed when KVM_CREATE_IRQCHIP is called
 - ensuring that a vcpu has an apic if it is installed after KVM_CREATE_IRQCHIP
 
 This is somewhat long winded because vcpu-arch.apic is created without
 kvm-lock held.

Hi Avi,

Thanks for following up on this. This looks OK to me.

I wonder if we will end up needing to add other sanity tests at the same
point, ie. when we install the vcpu, in which case we might need a
generic sanity hook. But better to keep it specific until we need
something generalised.

When we do irqchip-in-kernel on powerpc we'll need to rework the #ifdef
in kvm_host.h, because we don't want CONFIG_KVM_APIC_ARCHITECTURE, but
we will need our own kvm_vcpu_compatible(). But again we'll do that at
the time.

cheers



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