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Subject: Re: [PATCH] xen/events: don't use chip_data for legacy IRQs
To:     Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org,
        linux-kernel@vger.kernel.org
Cc:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        stable@vger.kernel.org
References: <20200930091614.13660-1-jgross@suse.com>
From:   Stefan Bader <stefan.bader@canonical.com>
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Message-ID: <1bf20485-3dd2-109f-5c8a-d2c971e1f6d6@canonical.com>
Date:   Wed, 30 Sep 2020 14:06:36 +0200
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On 30.09.20 11:16, 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 specifi=
c 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.
>=20
> Use a local array for this purpose in case of legacy IRQs, avoiding the=

> double use.
>=20
> Cc: stable@vger.kernel.org
> Fixes: c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data t=
o store a per interrupt XEN data pointer which contains XEN specific info=
rmation.")
> Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Stefan Bader <stefan.bader@canonical.com>
> ---
>  drivers/xen/events/events_base.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
>=20
> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/even=
ts_base.c
> index 90b8f56fbadb..6f02c18fa65c 100644
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -92,6 +92,8 @@ static bool (*pirq_needs_eoi)(unsigned irq);
>  /* Xen will never allocate port zero for any purpose. */
>  #define VALID_EVTCHN(chn)	((chn) !=3D 0)
> =20
> +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;
> @@ -156,7 +158,18 @@ int get_evtchn_to_irq(evtchn_port_t 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] =3D info;
> +	else
> +		irq_set_chip_data(irq, info);
>  }
> =20
>  /* Constructors for packed IRQ information. */
> @@ -377,7 +390,7 @@ static void xen_irq_init(unsigned irq)
>  	info->type =3D IRQT_UNBOUND;
>  	info->refcnt =3D -1;
> =20
> -	irq_set_chip_data(irq, info);
> +	set_info_for_irq(irq, info);
> =20
>  	list_add_tail(&info->list, &xen_irq_list_head);
>  }
> @@ -426,14 +439,14 @@ static int __must_check xen_allocate_irq_gsi(unsi=
gned gsi)
> =20
>  static void xen_free_irq(unsigned irq)
>  {
> -	struct irq_info *info =3D irq_get_chip_data(irq);
> +	struct irq_info *info =3D info_for_irq(irq);
> =20
>  	if (WARN_ON(!info))
>  		return;
> =20
>  	list_del(&info->list);
> =20
> -	irq_set_chip_data(irq, NULL);
> +	set_info_for_irq(irq, NULL);
> =20
>  	WARN_ON(info->refcnt > 0);
> =20
> @@ -603,7 +616,7 @@ EXPORT_SYMBOL_GPL(xen_irq_from_gsi);
>  static void __unbind_from_irq(unsigned int irq)
>  {
>  	evtchn_port_t evtchn =3D evtchn_from_irq(irq);
> -	struct irq_info *info =3D irq_get_chip_data(irq);
> +	struct irq_info *info =3D info_for_irq(irq);
> =20
>  	if (info->refcnt > 0) {
>  		info->refcnt--;
> @@ -1108,7 +1121,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
> =20
>  void unbind_from_irqhandler(unsigned int irq, void *dev_id)
>  {
> -	struct irq_info *info =3D irq_get_chip_data(irq);
> +	struct irq_info *info =3D info_for_irq(irq);
> =20
>  	if (WARN_ON(!info))
>  		return;
> @@ -1142,7 +1155,7 @@ int evtchn_make_refcounted(evtchn_port_t evtchn)
>  	if (irq =3D=3D -1)
>  		return -ENOENT;
> =20
> -	info =3D irq_get_chip_data(irq);
> +	info =3D info_for_irq(irq);
> =20
>  	if (!info)
>  		return -ENOENT;
> @@ -1170,7 +1183,7 @@ int evtchn_get(evtchn_port_t evtchn)
>  	if (irq =3D=3D -1)
>  		goto done;
> =20
> -	info =3D irq_get_chip_data(irq);
> +	info =3D info_for_irq(irq);
> =20
>  	if (!info)
>  		goto done;
>=20


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