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SubjectRe: [PATCH] iommu: Relax ACS requirement for Intel RCiEP devices.
Hi Alex

On Tue, May 26, 2020 at 05:07:15PM -0600, Alex Williamson wrote:
> > ---
> > drivers/iommu/iommu.c | 13 ++++++++++++-
> > 1 file changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 2b471419e26c..31b595dfedde 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -1187,7 +1187,18 @@ static struct iommu_group *get_pci_function_alias_group(struct pci_dev *pdev,
> > struct pci_dev *tmp = NULL;
> > struct iommu_group *group;
> >
> > - if (!pdev->multifunction || pci_acs_enabled(pdev, REQ_ACS_FLAGS))
> > + /*
> > + * Intel VT-d Specification Section 3.16, Root-Complex Peer to Peer
> > + * Considerations manadate that all transactions in RCiEP's and
> > + * even Integrated MFD's *must* be sent up to the IOMMU. P2P is
> > + * only possible on translated addresses. This gives enough
> > + * guarantee that such devices can be forgiven for lack of ACS
> > + * support.
> > + */
> > + if (!pdev->multifunction ||
> > + (pdev->vendor == PCI_VENDOR_ID_INTEL &&
> > + pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END) ||
> > + pci_acs_enabled(pdev, REQ_ACS_FLAGS))
> > return NULL;
> >
> > for_each_pci_dev(tmp) {
>
> Hi Ashok,
>
> As this is an Intel/VT-d standard, not a PCIe standard, why not
> implement this in pci_dev_specific_acs_enabled() with all the other
> quirks? Thanks,

Yes, that sounds like the right place.. I have a new patch, once its tested
i'll resend it. Thanks for pointing it out.

Cheers,
Ashok

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