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.d...@linaro.org>

> Signed-off-by: Marc Zyngier <marc.zyng...@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
> 

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