Marcelo Tosatti wrote:
On Thu, Feb 05, 2009 at 05:05:01PM +0100, Carsten Otte wrote:
KVM common code should'nt try to create the same virtual cpu twice.
In case of s390, it crashes badly in kvm_arch_vcpu_create.
Reported-by: Mijo Safradin <mijo@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Carsten Otte <cotte@xxxxxxxxxx>
---
virt/kvm/kvm_main.c | 3 +++
1 file changed, 3 insertions(+)
Index: kvm/virt/kvm/kvm_main.c
===================================================================
--- kvm.orig/virt/kvm/kvm_main.c
+++ kvm/virt/kvm/kvm_main.c
@@ -1605,6 +1605,9 @@ static int kvm_vm_ioctl_create_vcpu(stru
if (!valid_vcpu(n))
return -EINVAL;
+ if (kvm->vcpus[i])
+ return -EEXIST;
+
vcpu = kvm_arch_vcpu_create(kvm, n);
if (IS_ERR(vcpu))
return PTR_ERR(vcpu);
Its confusing that there is the exact same check below, with kvm->lock
held, and that both are needed since assignment happens under the lock.
Right, also the proposed fix still leaves a race.
Can you also make it straightforward while fixing the bug please.
Probably just hold it all the way through kvm_vm_ioctl_create_vcpu? Or
is that not possible?
The original intent was that kvm_arch_vcpu_create() not "link in" the
vcpu to any registers. That allows most of the vcpu creation to happen
outside a lock.
If it's not doable for s390 we can give this up, but I suggest checking
if it's possible to keep things as is and modify s390's
kvm_arch_vcpu_create() not to screw up instead.
--
error compiling committee.c: too many arguments to function
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