Re: [PATCH v2 10/11] vpci: Add initial support for virtual PCI bus topology

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.09.2021 09:48, Michal Orzel wrote:
> On 23.09.2021 14:55, Oleksandr Andrushchenko wrote:
>> --- a/xen/drivers/passthrough/pci.c
>> +++ b/xen/drivers/passthrough/pci.c
>> @@ -833,6 +833,63 @@ int pci_remove_device(u16 seg, u8 bus, u8 devfn)
>>      return ret;
>>  }
>>  
>> +static struct vpci_dev *pci_find_virtual_device(const struct domain *d,
>> +                                                const struct pci_dev *pdev)
>> +{
>> +    struct vpci_dev *vdev;
>> +
>> +    list_for_each_entry ( vdev, &d->vdev_list, list )
>> +        if ( vdev->pdev == pdev )
>> +            return vdev;
>> +    return NULL;
>> +}
>> +
>> +int pci_add_virtual_device(struct domain *d, const struct pci_dev *pdev)
>> +{
>> +    struct vpci_dev *vdev;
>> +
>> +    ASSERT(!pci_find_virtual_device(d, pdev));
>> +
>> +    /* Each PCI bus supports 32 devices/slots at max. */
>> +    if ( d->vpci_dev_next > 31 )
>> +        return -ENOSPC;
>> +
>> +    vdev = xzalloc(struct vpci_dev);
>> +    if ( !vdev )
>> +        return -ENOMEM;
>> +
>> +    /* We emulate a single host bridge for the guest, so segment is always 
>> 0. */
>> +    *(u16*) &vdev->seg = 0;
> Empty line hear would improve readability due to the asterisks being so close 
> to each other.
> Apart from that:
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
>> +    /*
>> +     * The bus number is set to 0, so virtual devices are seen
>> +     * as embedded endpoints behind the root complex.
>> +     */
>> +    *((u8*) &vdev->bus) = 0;
>> +    *((u8*) &vdev->devfn) = PCI_DEVFN(d->vpci_dev_next++, 0);

All of these casts are (a) malformed and (b) unnecessary in the first
place, afaics at least.

Jan