Re: [PATCH 2/2] vmd: Synchronize with RCU freeing msi irq descs

[Jon Derrick <jonathan.derrick@intel.com>]

Hi Bjorn,
Any chance of pulling this one in?

Thanks,
Jon

On Mon, Aug 08, 2016 at 10:47:21AM -0600, Jon Derrick wrote:
> This one's fine
> 
> Acked-by Jon Derrick: <jonathan.derrick@intel.com>
> 
> 
> On Thu, Aug 04, 2016 at 04:09:09PM -0600, Keith Busch wrote:
> > This patch fixes a potential race when disabling MSI/MSI-x on a VMD domain
> > device. If the vmd interrupt service is running, it may see a disabled
> > irq. We can synchronize rcu just before freeing the msi descriptor. This
> > is safe since the irq_desc lock isn't held, and the descriptor is valid
> > even though it is disabled. After vmd_msi_free, though, the handler is
> > reinitialiazed to handle_bad_irq, so we can't let the vmd isr's list
> > iteration see the disabled irq after this.
> > 
> > Signed-off-by: Keith Busch <keith.busch@intel.com>
> > ---
> >  arch/x86/pci/vmd.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/x86/pci/vmd.c b/arch/x86/pci/vmd.c
> > index 2294907..e3c9b9e 100644
> > --- a/arch/x86/pci/vmd.c
> > +++ b/arch/x86/pci/vmd.c
> > @@ -213,6 +213,8 @@ static void vmd_msi_free(struct irq_domain *domain,
> >  	struct vmd_irq *vmdirq = irq_get_chip_data(virq);
> >  	unsigned long flags;
> >  
> > +	synchronize_rcu();
> > +
> >  	/* XXX: Potential optimization to rebalance */
> >  	raw_spin_lock_irqsave(&list_lock, flags);
> >  	vmdirq->irq->count--;
> > -- 
> > 2.7.2
> > 
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