On 10.02.25 12:56, Jan Beulich wrote:
> On 10.02.2025 11:30, Mykyta Poturai wrote:
>> From: Stewart Hildebrand <stewart.hildebr...@amd.com>
>>
>> Enable the use of IOMMU + PCI in dom0 without having to specify
>> "pci-passthrough=yes".
>
> Why? It _is_ passing through, even if Dom0 is special.
Do you think it would be better to drop this completely and require
pci-passthrough=yes for PCI to work in Dom0?
>
>> @@ -83,9 +84,9 @@ static int __init pci_init(void)
>> {
>> /*
>> * Enable PCI passthrough when has been enabled explicitly
>> - * (pci-passthrough=on).
>> + * (pci-passthrough=on) or IOMMU is present and enabled.
>> */
>> - if ( !pci_passthrough_enabled )
>> + if ( !is_pci_passthrough_enabled() && !iommu_enabled )
>> return 0;
>
> I can't reasonably judge on this adjustment, but ...
>
>> --- a/xen/drivers/pci/physdev.c
>> +++ b/xen/drivers/pci/physdev.c
>> @@ -19,7 +19,7 @@ ret_t pci_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void)
>> arg)
>> struct pci_dev_info pdev_info;
>> nodeid_t node = NUMA_NO_NODE;
>>
>> - if ( !is_pci_passthrough_enabled() )
>> + if ( !is_pci_passthrough_enabled() && !iommu_enabled )
>> return -EOPNOTSUPP;
>>
>> ret = -EFAULT;
>> @@ -57,7 +57,7 @@ ret_t pci_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void)
>> arg)
>> case PHYSDEVOP_pci_device_remove: {
>> struct physdev_pci_device dev;
>>
>> - if ( !is_pci_passthrough_enabled() )
>> + if ( !is_pci_passthrough_enabled() && !iommu_enabled )
>> return -EOPNOTSUPP;
>>
>> ret = -EFAULT;
>
> ... these two certainly look wrong to be made. If an Arm-specific adjustment
> is needed (and can be justified), a per-arch hook may need introducing.
This should not affect x86 in any way if I'm not missing something, as
!is_pci_passthrough_enabled() will always be false. Or are you concerned
about something else?
>
> Jan
--
Mykyta
