On Tue, Jul 01, 2025 at 01:29:05PM -0600, Alex Williamson wrote:
> On Mon, 30 Jun 2025 19:28:33 -0300
> Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index d265de874b14b6..f4584ffacbc03d 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -65,8 +65,16 @@ struct iommu_group {
> > struct list_head entry;
> > unsigned int owner_cnt;
> > void *owner;
> > +
> > + /* Used by the device_group() callbacks */
> > + u32 bus_data;
> > };
> >
> > +/*
> > + * Everything downstream of this group should share it.
> > + */
> > +#define BUS_DATA_PCI_UNISOLATED BIT(0)
>
> NON_ISOLATED for consistency w/ enum from the previous patch?
Yes
> > - /* No shared group found, allocate new */
> > - return iommu_group_alloc();
> > + switch (pci_bus_isolated(pdev->bus)) {
> > + case PCIE_ISOLATED:
> > + /* Check multi-function groups and same-bus devfn aliases */
> > + group = pci_get_alias_group(pdev);
> > + if (group)
> > + return group;
> > +
> > + /* No shared group found, allocate new */
> > + return iommu_group_alloc();
>
> I'm not following how we'd handle a multi-function root port w/o
> consistent ACS isolation here. How/where does the resulting group get
> the UNISOLATED flag set?
Still wobbly on the root port/root bus.. So the answer is probably
that it doesn't.
What does a multi-function root port with different ACS flags even
mean and how should we treat it? I had in mind that the first root
port is the TA and immediately goes the IOMMU.
If you can explain a bit more about how you see the root ports working
I can try to make an implementation.
AFAICT the spec sort of says 'implementation defined' for ACS on root
ports??
Thanks,
Jason
