Re: [Xen-devel] [PATCH v6 19/36] ARM: VGIC: add vcpu_id to struct pending_irq

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 04/07/2017 06:32 PM, Andre Przywara wrote:
> The target CPU for an LPI is encoded in the interrupt translation table
> entry, so can't be easily derived from just an LPI number (short of
> walking *all* tables and find the matching LPI).
> To avoid this in case we need to know the VCPU (for the INVALL command,
> for instance), put the VCPU ID in the struct pending_irq, so that it is
> easily accessible.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
>  xen/include/asm-arm/vgic.h | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
> index 86a1a89..9145b42 100644
> --- a/xen/include/asm-arm/vgic.h
> +++ b/xen/include/asm-arm/vgic.h
> @@ -88,6 +88,9 @@ struct pending_irq
>       * TODO: when implementing irq migration, taking only the current
>       * vgic lock is not going to be enough. */
>      struct list_head lr_queue;
> +#ifdef CONFIG_HAS_ITS
> +    uint16_t lpi_vcpu_id;          /* The VCPU for an LPI. */
> +#endif
I am sorry, but in the current state this is a nack from me side. The 
pending_irq structure will increase by 8 bytes because of the alignment.
This will affect all the irq_pending as soon as CONFIG_HAS_ITS is 
enabled even if the platform is not using ITS.
Looking at the current usage it is only used by INVALL, which lead to 
confirm my first nack.
Please either find a hole in pending_irq or find an alternative solution.

Cheers,

--
Julien Grall

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