Re: [PATCH v5 11/14] vpci: add initial support for virtual PCI bus topology

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.11.2021 12:02, Oleksandr Andrushchenko wrote:
> @@ -145,6 +148,53 @@ int vpci_add_handlers(struct pci_dev *pdev)
>  }
>  
>  #ifdef CONFIG_HAS_VPCI_GUEST_SUPPORT
> +int vpci_add_virtual_device(struct pci_dev *pdev)
> +{
> +    struct domain *d = pdev->domain;
> +    pci_sbdf_t sbdf = { 0 };
> +    unsigned long new_dev_number;
> +
> +    /*
> +     * Each PCI bus supports 32 devices/slots at max or up to 256 when
> +     * there are multi-function ones which are not yet supported.
> +     */
> +    if ( pdev->info.is_extfn )
> +    {
> +        gdprintk(XENLOG_ERR, "%pp: only function 0 passthrough supported\n",
> +                 &pdev->sbdf);
> +        return -EOPNOTSUPP;
> +    }
> +
> +    new_dev_number = find_first_zero_bit(&d->vpci_dev_assigned_map,
> +                                         VPCI_MAX_VIRT_DEV);
> +    if ( new_dev_number >= VPCI_MAX_VIRT_DEV )
> +        return -ENOSPC;
> +
> +    __set_bit(new_dev_number, &d->vpci_dev_assigned_map);
> +
> +    /*
> +     * Both segment and bus number are 0:
> +     *  - we emulate a single host bridge for the guest, e.g. segment 0
> +     *  - with bus 0 the virtual devices are seen as embedded
> +     *    endpoints behind the root complex
> +     *
> +     * TODO: add support for multi-function devices.
> +     */
> +    sbdf.devfn = PCI_DEVFN(new_dev_number, 0);
> +    pdev->vpci->guest_sbdf = sbdf;
> +
> +    return 0;
> +
> +}
> +REGISTER_VPCI_INIT(vpci_add_virtual_device, VPCI_PRIORITY_MIDDLE);

Is this function guaranteed to always be invoked ahead of ...

> +static void vpci_remove_virtual_device(struct domain *d,
> +                                       const struct pci_dev *pdev)
> +{
> +    __clear_bit(pdev->vpci->guest_sbdf.dev, &d->vpci_dev_assigned_map);
> +    pdev->vpci->guest_sbdf.sbdf = ~0;
> +}

... this one, even when considering error paths? Otherwise you may
wrongly clear bit 31 here afaict.

Jan