Re: [PATCH v12 11/15] vpci: add initial support for virtual PCI bus topology

[George Dunlap <george.dunlap@xxxxxxxxx>]

On Tue, Jan 9, 2024 at 9:54 PM Stewart Hildebrand
<stewart.hildebrand@xxxxxxx> wrote:
> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
> index 37f5922f3206..b58a822847be 100644
> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -484,6 +484,14 @@ struct domain
>       * 2. pdev->vpci->lock
>       */
>      rwlock_t pci_lock;
> +#ifdef CONFIG_HAS_VPCI_GUEST_SUPPORT
> +    /*
> +     * The bitmap which shows which device numbers are already used by the
> +     * virtual PCI bus topology and is used to assign a unique SBDF to the
> +     * next passed through virtual PCI device.
> +     */
> +    DECLARE_BITMAP(vpci_dev_assigned_map, VPCI_MAX_VIRT_DEV);
> +#endif
>  #endif

Without digging through the whole series, how big do we expect this
bitmap to be on typical systems?

If it's only going to be a handful of bytes, keeping it around for all
guests would be OK; but it's large, it would be better as a pointer,
since it's unused on the vast majority of guests.

 -George