Re: [RFC KERNEL PATCH v2 2/3] xen/pvh: Unmask irq for passthrough device in PVH dom0

[Thomas Gleixner]

On Fri, Nov 24 2023 at 18:31, Jiqian Chen wrote:
> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> index 5a96b6c66c07..b83d02bcc76c 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -357,6 +357,7 @@ static int pcistub_match(struct pci_dev *dev)
>  static int pcistub_init_device(struct pci_dev *dev)
>  {
>  	struct xen_pcibk_dev_data *dev_data;
> +	struct irq_desc *desc = NULL;
>  	int err = 0;
>  
>  	dev_dbg(&dev->dev, "initializing...\n");
> @@ -399,6 +400,12 @@ static int pcistub_init_device(struct pci_dev *dev)
>  	if (err)
>  		goto config_release;
>  
> +	if (xen_initial_domain() && xen_pvh_domain()) {
> +		if (dev->irq <= 0 || !(desc = irq_to_desc(dev->irq)))

Driver code has absolutely no business to access irq_desc.

> +			goto config_release;
> +		unmask_irq(desc);

Or to invoke any internal function.

> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -439,6 +439,7 @@ void unmask_irq(struct irq_desc *desc)
>  		irq_state_clr_masked(desc);
>  	}
>  }
> +EXPORT_SYMBOL_GPL(unmask_irq);

Not going to happen.

> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -380,7 +380,7 @@ struct irq_desc *irq_to_desc(unsigned int irq)
>  {
>  	return mtree_load(&sparse_irqs, irq);
>  }
> -#ifdef CONFIG_KVM_BOOK3S_64_HV_MODULE
> +#if defined CONFIG_KVM_BOOK3S_64_HV_MODULE || defined CONFIG_XEN_PVH

Neither that.

This all smells badly like a XEN internal issue and we are not going to
hack around it by exposing interrupt internals.

Thanks,

        tglx