On 28.08.2023 19:56, Stewart Hildebrand wrote:
> Currently, Xen vPCI only supports virtualizing the MSI and MSI-X capabilities.
> Hide all other PCI capabilities (including extended capabilities) from domUs
> for
> now, even though there may be certain devices/drivers that depend on being
> able
> to discover certain capabilities.
>
> We parse the physical PCI capabilities linked list and add vPCI register
> handlers for the next elements, inserting our own next value, thus presenting
> a
> modified linked list to the domU.
>
> Introduce helper functions vpci_hw_read8 and vpci_read_val. The vpci_read_val
> helper function returns a fixed value, which may be used for RAZ registers, or
> registers whose value doesn't change.
>
> Introduce pci_find_next_cap_ttl() helper while adapting the logic from
> pci_find_next_cap() to suit our needs, and implement the existing
> pci_find_next_cap() in terms of the new helper.
>
> Signed-off-by: Stewart Hildebrand <stewart.hildebr...@amd.com>
Reviewed-by: Jan Beulich <jbeul...@suse.com>
Nevertheless a couple of remarks:
> --- a/xen/drivers/pci/pci.c
> +++ b/xen/drivers/pci/pci.c
> @@ -39,31 +39,44 @@ unsigned int pci_find_cap_offset(pci_sbdf_t sbdf,
> unsigned int cap)
> return 0;
> }
>
> -unsigned int pci_find_next_cap(pci_sbdf_t sbdf, unsigned int pos,
> - unsigned int cap)
> +unsigned int pci_find_next_cap_ttl(pci_sbdf_t sbdf, unsigned int pos,
> + bool (*is_match)(unsigned int, unsigned
> int),
> + unsigned int userdata, unsigned int *ttl)
> {
> - u8 id;
> - int ttl = 48;
> + unsigned int id;
>
> - while ( ttl-- )
> + while ( (*ttl)-- )
> {
> pos = pci_conf_read8(sbdf, pos);
> if ( pos < 0x40 )
> break;
>
> - pos &= ~3;
> - id = pci_conf_read8(sbdf, pos + PCI_CAP_LIST_ID);
> + id = pci_conf_read8(sbdf, (pos & ~3) + PCI_CAP_LIST_ID);
>
> if ( id == 0xff )
> break;
> - if ( id == cap )
> + if ( is_match(id, userdata) )
> return pos;
>
> - pos += PCI_CAP_LIST_NEXT;
> + pos = (pos & ~3) + PCI_CAP_LIST_NEXT;
> }
> +
> return 0;
> }
>
> +static bool cf_check is_cap_match(unsigned int id1, unsigned int id2)
> +{
> + return id1 == id2;
> +}
Personally I would have preferred to get away without yet another hook
function here, by ...
> +unsigned int pci_find_next_cap(pci_sbdf_t sbdf, unsigned int pos,
> + unsigned int cap)
> +{
> + unsigned int ttl = 48;
> +
> + return pci_find_next_cap_ttl(sbdf, pos, is_cap_match, cap, &ttl) & ~3;
... passing NULL here and then suitably handling the case in that
common helper.
> @@ -561,6 +573,71 @@ static int cf_check init_bars(struct pci_dev *pdev)
> if ( rc )
> return rc;
>
> + if ( !is_hardware_domain(pdev->domain) )
> + {
> + if ( !(pci_conf_read16(pdev->sbdf, PCI_STATUS) &
> PCI_STATUS_CAP_LIST) )
> + {
> + /* RAZ/WI */
> + rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL,
> + PCI_CAPABILITY_LIST, 1, (void *)0);
> + if ( rc )
> + return rc;
> + }
> + else
> + {
> + /* Only expose capabilities to the guest that vPCI can handle. */
> + uint8_t next;
If this was "unsigned long", ...
> + unsigned int ttl = 48;
> +
> + next = pci_find_next_cap_ttl(pdev->sbdf, PCI_CAPABILITY_LIST,
> + vpci_cap_supported, 0, &ttl);
> +
> + rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL,
> + PCI_CAPABILITY_LIST, 1,
> + (void *)(uintptr_t)next);
... you'd avoid the need for the double cast here and again below. Yet
then I realize that Misra would take offence at us doing so ...
Jan
