Re: [PATCH v5 01/26] irqchip/gic-v3-its: Setup VLPI properties at map time

Christoffer Dall
2017-10-30T06:45:11Z

On Fri, Oct 27, 2017 at 03:28:30PM +0100, Marc Zyngier wrote:
> So far, we require the hypervisor to update the VLPI properties
> once the the VLPI mapping has been established. While this
> makes it easy for the ITS driver, it creates a window where
> an incoming interrupt can be delivered with an unknown set
> of properties. Not very nice.
>
> Instead, let's add a "properties" field to the mapping structure,
> and use that to configure the VLPI before it actually gets mapped.
>

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> drivers/irqchip/irq-gic-v3-its.c | 19 +++++++++++++++++--
> include/linux/irqchip/arm-gic-v4.h | 2 ++
> 2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 85f47ef4f1f7..2c4074c97454 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1006,9 +1006,15 @@ static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
> if (irqd_is_forwarded_to_vcpu(d)) {
> struct its_device *its_dev = irq_data_get_irq_chip_data(d);
> u32 event = its_get_event_id(d);
> + struct its_vlpi_map *map;
>
> prop_page = its_dev->event_map.vm->vprop_page;
> - hwirq = its_dev->event_map.vlpi_maps[event].vintid;
> + map = &its_dev->event_map.vlpi_maps[event];
> + hwirq = map->vintid;
> +
> + /* Remember the updated property */
> + map->properties &= ~clr;
> + map->properties |= set | LPI_PROP_GROUP1;
> } else {
> prop_page = gic_rdists->prop_page;
> hwirq = d->hwirq;
> @@ -1018,6 +1024,7 @@ static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
> *cfg &= ~clr;
> *cfg |= set | LPI_PROP_GROUP1;
>
> +
> /*
> * Make the above write visible to the redistributors.
> * And yes, we're flushing exactly: One. Single. Byte.
> @@ -1238,12 +1245,20 @@ static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
> /* Ensure all the VPEs are mapped on this ITS */
> its_map_vm(its_dev->its, info->map->vm);
>
> + /*
> + * Flag the interrupt as forwarded so that we can
> + * start poking the virtual property table.
> + */
> + irqd_set_forwarded_to_vcpu(d);
> +
> + /* Write out the property to the prop table */
> + lpi_write_config(d, 0xff, info->map->properties);
> +
> /* Drop the physical mapping */
> its_send_discard(its_dev, event);
>
> /* and install the virtual one */
> its_send_vmapti(its_dev, event);
> - irqd_set_forwarded_to_vcpu(d);
>
> /* Increment the number of VLPIs */
> its_dev->event_map.nr_vlpis++;
> diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
> index 43cde15f221b..447da8ca2156 100644
> --- a/include/linux/irqchip/arm-gic-v4.h
> +++ b/include/linux/irqchip/arm-gic-v4.h
> @@ -71,12 +71,14 @@ struct its_vpe {
> * @vm: Pointer to the GICv4 notion of a VM
> * @vpe: Pointer to the GICv4 notion of a virtual CPU (VPE)
> * @vintid: Virtual LPI number
> + * @properties: Priority and enable bits (as written in the prop table)
> * @db_enabled: Is the VPE doorbell to be generated?
> */
> struct its_vlpi_map {
> struct its_vm *vm;
> struct its_vpe *vpe;
> u32 vintid;
> + u8 properties;
> bool db_enabled;
> };
>
> --
> 2.11.0
>