Re: [Xen-devel] [PATCH v3 6/9] xen/vpci: trap access to the list of PCI capabilities

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.04.17 at 16:35, <roger.pau@xxxxxxxxxx> wrote:
> +static int vpci_index_capabilities(struct pci_dev *pdev)
> +{
> +    uint8_t seg = pdev->seg, bus = pdev->bus;
> +    uint8_t slot = PCI_SLOT(pdev->devfn), func = PCI_FUNC(pdev->devfn);
> +    uint8_t pos = PCI_CAPABILITY_LIST;
> +    uint16_t status;
> +    unsigned int max_cap = 48;
> +    struct vpci_capability *cap;
> +    int rc;
> +
> +    INIT_LIST_HEAD(&pdev->vpci->cap_list);
> +
> +    /* Check if device has capabilities. */
> +    status = pci_conf_read16(seg, bus, slot, func, PCI_STATUS);
> +    if ( !(status & PCI_STATUS_CAP_LIST) )
> +        return 0;
> +
> +    /* Add the root capability pointer. */
> +    cap = xzalloc(struct vpci_capability);
> +    if ( !cap )
> +        return -ENOMEM;
> +
> +    cap->offset = pos;
> +    list_add_tail(&cap->next, &pdev->vpci->cap_list);
> +    rc = xen_vpci_add_register(pdev, vpci_cap_read, vpci_cap_write, pos,
> +                               1, cap);
> +    if ( rc )
> +        return rc;
> +
> +    /*
> +     * Iterate over the list of capabilities present in the device, and
> +     * add a handler for each register pointer to the next item
> +     * (PCI_CAP_LIST_NEXT).
> +     */
> +    while ( max_cap-- )
> +    {
> +        pos = pci_conf_read8(seg, bus, slot, func, pos);
> +        if ( pos < 0x40 )
> +            break;
> +
> +        cap = xzalloc(struct vpci_capability);
> +        if ( !cap )
> +            return -ENOMEM;
> +
> +        cap->offset = pos;
> +        list_add_tail(&cap->next, &pdev->vpci->cap_list);
> +        pos += PCI_CAP_LIST_NEXT;
> +        rc = xen_vpci_add_register(pdev, vpci_cap_read, vpci_cap_write, pos,
> +                                   1, cap);
> +        if ( rc )
> +            return rc;
> +    }
> +
> +    return 0;
> +}

Btw., instead of duplicating some of what pci_find_cap_offset()
and pci_find_next_cap() do, perhaps worth making those two
functions capable of dealing with a wildcard ID (0xff) as input.

Jan


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