On Mon, Feb 28, 2022 at 08:50:51AM +0800, Lu Baolu wrote: > If a switch lacks ACS P2P Request Redirect, a device below the switch can > bypass the IOMMU and DMA directly to other devices below the switch, so > all the downstream devices must be in the same IOMMU group as the switch > itself. > > The existing VFIO framework allows the portdrv driver to be bound to the > bridge while its downstream devices are assigned to user space. The > pci_dma_configure() marks the IOMMU group as containing only devices > with kernel drivers that manage DMA. Avoid this default behavior for the > portdrv driver in order for compatibility with the current VFIO usage.
It would be nice to explicitly say here how we can look at portdrv (and pci_stub) and conclude that ".driver_managed_dma = true" is safe. Otherwise I won't know what kind of future change to portdrv might make it unsafe. > Suggested-by: Jason Gunthorpe <[email protected]> > Suggested-by: Kevin Tian <[email protected]> > Signed-off-by: Lu Baolu <[email protected]> > Reviewed-by: Jason Gunthorpe <[email protected]> Acked-by: Bjorn Helgaas <[email protected]> > --- > drivers/pci/pcie/portdrv_pci.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c > index 35eca6277a96..6b2adb678c21 100644 > --- a/drivers/pci/pcie/portdrv_pci.c > +++ b/drivers/pci/pcie/portdrv_pci.c > @@ -202,6 +202,8 @@ static struct pci_driver pcie_portdriver = { > > .err_handler = &pcie_portdrv_err_handler, > > + .driver_managed_dma = true, > + > .driver.pm = PCIE_PORTDRV_PM_OPS, > }; > > -- > 2.25.1 > > _______________________________________________ > iommu mailing list > [email protected] > https://lists.linuxfoundation.org/mailman/listinfo/iommu _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
