Hi Julien,
> On 25 Jun 2023, at 1:56 pm, Julien Grall <jul...@xen.org> wrote:
>
> Hi,
>
> On 15/06/2023 22:05, Stewart Hildebrand wrote:
>> On 6/7/23 03:19, Julien Grall wrote:
>>> On 07/06/2023 04:02, Stewart Hildebrand wrote:
>>>> This series introduces SMMU handling for PCIe passthrough on ARM. These
>>>> patches
>>>> are independent from (and don't depend on) the vPCI reference
>>>> counting/locking
>>>> work in progress, and should be able to be upstreamed independently.
>>>
>>> Can you clarify how this code was tested? Does this require code not yet
>>> upstreamed?
>> I'm testing the series standalone (+ config changes) by using a PCI device
>> in dom0, and also in combination with the vPCI series [3] [4] for
>> passthrough to a domU.
>> Here are some more details on the test cases I'm using.
>
> Thanks that's helpful! One comment about the first test case.
>
>> 1. Using the PCI device in dom0 with the pci-passthrough=yes arg. In this
>> case a couple of additional config changes [1] [2] are needed to select
>> CONFIG_HAS_PCI=y, CONFIG_HAS_VPCI=y, and make has_vpci() return true. Aside
>> from this series itself and the config changes, nothing else
>> not-yet-upstreamed is required for this test case. It is on my TODO list to
>> upstream these config changes, which I think will be useful on their own,
>> not necessarily as part of any other series.
>
> I find a bit confusing that the IOMMU support for dom0 is gated behind
> 'pci-passthrough'. I was expecting that the iommu would also be properly
> configured for PCI if we using 'iommu=yes'.
As per my understanding Xen can configure the iommus for PCI device without
"pci-passthroughâ enabled
if we follow below path:
1) PCI host bridge is already enumerated and powered on in firmware before
Xen boot
2) PCI devices are scanned in Xen.
(https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc/-/commit/bce463e1588a45e1bfdf59fc0d5f88b16604e439)
3) After scanning the PCI devices add PCI devices to iommu (
iommu_add_device() )
If PCI host bridge is not enumerated then we need "pci-passthroughâ enabled to
allow Linux to do
enumeration and to inform Xen via PHYSDEVOP_pci_device_add hyper call to add
PCI devices in Xen
This is implemented as part of PCI passthrough feature.
Regards,
Rahul
