Re: [Xen-devel] [PATCH v3 4/4] iommu / pci: re-implement XEN_DOMCTL_get_device_group...

[Jan Beulich <JBeulich@xxxxxxxx>]

On 16.07.2019 12:16, Paul Durrant wrote:
> +int iommu_get_device_group(struct domain *d, pci_sbdf_t sbdf,
> +                           XEN_GUEST_HANDLE_64(uint32) buf,
> +                           unsigned int max_sdevs)
> +{
> +    struct iommu_group *grp = NULL;
> +    struct pci_dev *pdev;
> +    unsigned int i = 0;
> +
> +    pcidevs_lock();
> +
> +    for_each_pdev ( d, pdev )
> +    {
> +        if ( pdev->sbdf.sbdf == sbdf.sbdf )
> +        {
> +            grp = pdev->grp;
> +            break;
> +        }
> +    }
> +
> +    if ( !grp )
> +        goto out;
> +
> +    for_each_pdev ( d, pdev )
> +    {
> +        if ( xsm_get_device_group(XSM_HOOK, pdev->sbdf.sbdf) ||
> +             pdev->grp != grp )
> +            continue;
> +
> +        if ( i < max_sdevs &&
> +             unlikely(copy_to_guest_offset(buf, i++, &pdev->sbdf.sbdf, 1)) )

If you want to avoid breaking existing callers, you'll have to mimic
here ...

> -static int iommu_get_device_group(
> -    struct domain *d, u16 seg, u8 bus, u8 devfn,
> -    XEN_GUEST_HANDLE_64(uint32) buf, int max_sdevs)
> -{
> -    const struct domain_iommu *hd = dom_iommu(d);
> -    struct pci_dev *pdev;
> -    int group_id, sdev_id;
> -    u32 bdf;
> -    int i = 0;
> -    const struct iommu_ops *ops = hd->platform_ops;
> -
> -    if ( !iommu_enabled || !ops || !ops->get_device_group_id )
> -        return 0;
> -
> -    group_id = ops->get_device_group_id(seg, bus, devfn);
> -
> -    pcidevs_lock();
> -    for_each_pdev( d, pdev )
> -    {
> -        if ( (pdev->seg != seg) ||
> -             ((pdev->bus == bus) && (pdev->devfn == devfn)) )
> -            continue;
> -
> -        if ( xsm_get_device_group(XSM_HOOK, (seg << 16) | (pdev->bus << 8) | 
> pdev->devfn) )
> -            continue;
> -
> -        sdev_id = ops->get_device_group_id(seg, pdev->bus, pdev->devfn);
> -        if ( (sdev_id == group_id) && (i < max_sdevs) )
> -        {
> -            bdf = 0;
> -            bdf |= (pdev->bus & 0xff) << 16;
> -            bdf |= (pdev->devfn & 0xff) << 8;
> -
> -            if ( unlikely(copy_to_guest_offset(buf, i, &bdf, 1)) )

... this rather odd organization of BDF. Omitting the segment is, I
think, fine, as I don't expect groups to extend past segment
boundaries (and iirc neither Intel's nor AMD's implementation have
any means for this to happen).

Jan
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