Re: [PATCH] xen/events: don't use chip_data for legacy IRQs

[Jürgen Groß <jgross@xxxxxxxx>]

Any reason this has not made it into 5.4.y and older by now?

This patch is fixing a real problem...


Juergen

On 05.10.20 08:19, Juergen Gross wrote:
> Since commit c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.")
> Xen is using the chip_data pointer for storing IRQ specific data. When
> running as a HVM domain this can result in problems for legacy IRQs, as
> those might use chip_data for their own purposes.
>
> Use a local array for this purpose in case of legacy IRQs, avoiding the
> double use.
>
> Fixes: c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Tested-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20200930091614.13660-1-jgross@xxxxxxxx
> ---
> This is a backport for stable kernel 5.4.y and older
> ---
>   drivers/xen/events/events_base.c | 29 +++++++++++++++++++++--------
>   1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
> index 55f2b834cf13..e402620b8920 100644
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -91,6 +91,8 @@ static bool (*pirq_needs_eoi)(unsigned irq);
>   /* Xen will never allocate port zero for any purpose. */
>   #define VALID_EVTCHN(chn)	((chn) != 0)
>   
> +static struct irq_info *legacy_info_ptrs[NR_IRQS_LEGACY];
> +
>   static struct irq_chip xen_dynamic_chip;
>   static struct irq_chip xen_percpu_chip;
>   static struct irq_chip xen_pirq_chip;
> @@ -155,7 +157,18 @@ int get_evtchn_to_irq(unsigned evtchn)
>   /* Get info for IRQ */
>   struct irq_info *info_for_irq(unsigned irq)
>   {
> -	return irq_get_chip_data(irq);
> +	if (irq < nr_legacy_irqs())
> +		return legacy_info_ptrs[irq];
> +	else
> +		return irq_get_chip_data(irq);
> +}
> +
> +static void set_info_for_irq(unsigned int irq, struct irq_info *info)
> +{
> +	if (irq < nr_legacy_irqs())
> +		legacy_info_ptrs[irq] = info;
> +	else
> +		irq_set_chip_data(irq, info);
>   }
>   
>   /* Constructors for packed IRQ information. */
> @@ -376,7 +389,7 @@ static void xen_irq_init(unsigned irq)
>   	info->type = IRQT_UNBOUND;
>   	info->refcnt = -1;
>   
> -	irq_set_chip_data(irq, info);
> +	set_info_for_irq(irq, info);
>   
>   	list_add_tail(&info->list, &xen_irq_list_head);
>   }
> @@ -425,14 +438,14 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi)
>   
>   static void xen_free_irq(unsigned irq)
>   {
> -	struct irq_info *info = irq_get_chip_data(irq);
> +	struct irq_info *info = info_for_irq(irq);
>   
>   	if (WARN_ON(!info))
>   		return;
>   
>   	list_del(&info->list);
>   
> -	irq_set_chip_data(irq, NULL);
> +	set_info_for_irq(irq, NULL);
>   
>   	WARN_ON(info->refcnt > 0);
>   
> @@ -602,7 +615,7 @@ EXPORT_SYMBOL_GPL(xen_irq_from_gsi);
>   static void __unbind_from_irq(unsigned int irq)
>   {
>   	int evtchn = evtchn_from_irq(irq);
> -	struct irq_info *info = irq_get_chip_data(irq);
> +	struct irq_info *info = info_for_irq(irq);
>   
>   	if (info->refcnt > 0) {
>   		info->refcnt--;
> @@ -1106,7 +1119,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
>   
>   void unbind_from_irqhandler(unsigned int irq, void *dev_id)
>   {
> -	struct irq_info *info = irq_get_chip_data(irq);
> +	struct irq_info *info = info_for_irq(irq);
>   
>   	if (WARN_ON(!info))
>   		return;
> @@ -1140,7 +1153,7 @@ int evtchn_make_refcounted(unsigned int evtchn)
>   	if (irq == -1)
>   		return -ENOENT;
>   
> -	info = irq_get_chip_data(irq);
> +	info = info_for_irq(irq);
>   
>   	if (!info)
>   		return -ENOENT;
> @@ -1168,7 +1181,7 @@ int evtchn_get(unsigned int evtchn)
>   	if (irq == -1)
>   		goto done;
>   
> -	info = irq_get_chip_data(irq);
> +	info = info_for_irq(irq);
>   
>   	if (!info)
>   		goto done;