Re: [PATCH 1/2] KVM: x86: Fix deadlock in kvm_vm_ioctl_set_msr_filter()

[Michal Luczaj <mhal@xxxxxxx>]

On 1/5/23 23:23, Sean Christopherson wrote:
> Ha!  Case in point.  The aforementioned Xen code blatantly violates KVM's locking
> rules:
> 
>   - kvm->lock is taken outside vcpu->mutex
> 

FWIW, I guess this looks like a violation of the same sort:

kvm_vcpu_ioctl()
  mutex_lock_killable(&vcpu->mutex)
  kvm_arch_vcpu_ioctl()
    kvm_xen_vcpu_get_attr() / kvm_xen_vcpu_set_attr()
      mutex_lock(&vcpu->kvm->lock)

> In other words, I'm find with this patch for optimization purposes, but I don't
> think we should call it a bug fix. (...)

Sure, resending as such, along with minor fixes.

thanks,
Michal