Re: [PATCH 0/3] KVM: Make kvm_lock non-raw

[Paul Gortmaker]

On 13-09-16 10:06 AM, Paolo Bonzini wrote:
> Paul Gortmaker reported a BUG on preempt-rt kernels, due to taking the
> mmu_lock within the raw kvm_lock in mmu_shrink_scan.  He provided a
> patch that shrunk the kvm_lock critical section so that the mmu_lock
> critical section does not nest with it, but in the end there is no reason
> for the vm_list to be protected by a raw spinlock.  Only manipulations
> of kvm_usage_count and the consequent hardware_enable/disable operations
> are not preemptable.
> 
> This small series thus splits the kvm_lock in the "raw" part and the
> "non-raw" part.
> 
> Paul, could you please provide your Tested-by?

Sure, I'll go back and see if I can find what triggered it in the
original report, and give the patches a spin on 3.4.x-rt (and probably
3.10.x-rt, since that is where rt-current is presently).

Paul.
--

> 
> Thanks,
> 
> Paolo
> 
> Paolo Bonzini (3):
>   KVM: cleanup (physical) CPU hotplug
>   KVM: protect kvm_usage_count with its own spinlock
>   KVM: Convert kvm_lock back to non-raw spinlock
> 
>  Documentation/virtual/kvm/locking.txt |  8 ++++--
>  arch/x86/kvm/mmu.c                    |  4 +--
>  arch/x86/kvm/x86.c                    |  8 +++---
>  include/linux/kvm_host.h              |  2 +-
>  virt/kvm/kvm_main.c                   | 51 ++++++++++++++++++-----------------
>  5 files changed, 40 insertions(+), 33 deletions(-)
> 
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