Re: [PATCH] kvm-kmod: fix kvm_request_irq race

[Avi Kivity <avi@redhat.com>]

Chris Wright wrote:
> Commit "32658734: Fix request_irq() for < 2.6.19" is racy between multiple
> guests since ioctl is only serialized per guest.  Add mutex and serialize
> kvm_request_irq/kvm_free_irq to avoid race.
>
> Signed-off-by: Chris Wright <chrisw@redhat.com>
> ---
>  external-module-compat-comm.h |   14 +++++++++++---
>  1 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/external-module-compat-comm.h b/external-module-compat-comm.h
> index 8cb5440..eaad986 100644
> --- a/external-module-compat-comm.h
> +++ b/external-module-compat-comm.h
> @@ -645,6 +645,7 @@ static inline int pci_reset_function(struct pci_dev *dev)
>  
>  typedef irqreturn_t (*kvm_irq_handler_t)(int, void *);
>  static kvm_irq_handler_t kvm_irq_handlers[NR_IRQS];
> +static DEFINE_MUTEX(kvm_irq_handlers_mutex);
>  
>   

Since this mutex is in a header file, it can be instantiated multiple 
times.  It will only serialize callers within a translation unit.  
Please define it in a C file.

Would be best to move the the code as well.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.