Re: [PATCH v11 08/16] genirq/msi: Provide msi_device_domain_restore_msi_msgs()

[Pranjal Shrivastava <praan@google.com>]

On Wed, Oct 14, 2026 at 11:58:21PM +0200, Thomas Gleixner wrote:
> On Tue, Sep 29 2026 at 03:45, Pranjal Shrivastava wrote:
> > +void msi_device_domain_restore_msi_msgs(struct device *dev, unsigned int domid)
> > +{
> > +	if (!dev->msi.data)
> > +		return;
> > +
> > +	guard(msi_descs_lock)(dev);
> > +	struct irq_domain *domain = msi_get_device_domain(dev, domid);
> > +
> > +	if (!domain || !irq_domain_is_msi_device(domain))
> > +		return;
> > +
> > +	struct xarray *xa = &dev->msi.data->__domains[domid].store;
> > +	struct msi_domain_info *info = domain->host_data;
> > +	struct msi_desc *msi_desc;
> > +	unsigned long idx;
> > +
> > +	xa_for_each_range(xa, idx, msi_desc, 0, info->hwsize - 1) {
> > +		/* Only handle MSI entries which have an interrupt associated */
> > +		if (!msi_desc_match(msi_desc, MSI_DESC_ASSOCIATED))
> > +			continue;
> > +
> > +		scoped_irqdesc_get_and_buslock(msi_desc->irq, 0) {
> > +			struct irq_data *data = irq_desc_get_irq_data(scoped_irqdesc);
> > +			struct msi_msg msg = msi_desc->msg;
> > +
> > +			if (data->chip)
> > +				irq_chip_write_msi_msg(data, &msg);
> > +		}
> > +	}
> 
> In this case sashiko is wrong:
> 
> > [Severity: Critical]
> > Will this result in a NULL pointer dereference in hierarchical IRQ domains?
> > 
> > Since irq_desc_get_irq_data() retrieves the top-level irq_data, data->chip
> > points to the top-level irq_chip. In hierarchical IRQ domains, the top-level
> > irq_chip typically does not implement the irq_write_msi_msg callback.
> > 
> > When this top-level irq_data is passed to irq_chip_write_msi_msg(), it will
> > dereference a NULL function pointer:
> 
> All MSI top level (device) domains implement the irq_write_msi_msg()
> callback. That's the whole point of the top level MSI domain as that's
> the one which has access to the device and the associated message store.
> 

Ack, I can try folding this into a comment to avoid sashiko reporting
this multiple time in the v12.

Thanks,
Praan