Re: [PATCH v2 3/7] PCI/ACS: Enable PCI_ACS_TB for untrusted/external-facing devices

[Rajat Jain <rajatja@google.com>]

On Mon, Jul 6, 2020 at 9:45 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Mon, Jun 29, 2020 at 09:49:39PM -0700, Rajat Jain wrote:
> > When enabling ACS, enable translation blocking for external facing ports
> > and untrusted devices.
> >
> > Signed-off-by: Rajat Jain <rajatja@google.com>
> > ---
> > v2: Commit log change
> >
> >  drivers/pci/pci.c    |  4 ++++
> >  drivers/pci/quirks.c | 11 +++++++++++
> >  2 files changed, 15 insertions(+)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index d2ff987585855..79853b52658a2 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -3330,6 +3330,10 @@ static void pci_std_enable_acs(struct pci_dev *dev)
> >       /* Upstream Forwarding */
> >       ctrl |= (cap & PCI_ACS_UF);
> >
> > +     if (dev->external_facing || dev->untrusted)
> > +             /* Translation Blocking */
> > +             ctrl |= (cap & PCI_ACS_TB);
> > +
> >       pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
> >  }
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index b341628e47527..6294adeac4049 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -4934,6 +4934,13 @@ static void pci_quirk_enable_intel_rp_mpc_acs(struct pci_dev *dev)
> >       }
> >  }
> >
> > +/*
> > + * Currently this quirk does the equivalent of
> > + * PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF | PCI_ACS_SV
> > + *
> > + * Currently missing, it also needs to do equivalent of PCI_ACS_TB,
> > + * if dev->external_facing || dev->untrusted
>
> I don't understand this comment.  Is this a "TODO"?  Is there
> something more that needs to be done here?

Yes. I'll mark it as a TODO to make it more clear.

>
> After a patch is applied, a comment should describe the code as it is.
>
> > + */
> >  static int pci_quirk_enable_intel_pch_acs(struct pci_dev *dev)
> >  {
> >       if (!pci_quirk_intel_pch_acs_match(dev))
> > @@ -4973,6 +4980,10 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
> >       ctrl |= (cap & PCI_ACS_CR);
> >       ctrl |= (cap & PCI_ACS_UF);
> >
> > +     if (dev->external_facing || dev->untrusted)
> > +             /* Translation Blocking */
> > +             ctrl |= (cap & PCI_ACS_TB);
> > +
> >       pci_write_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, ctrl);
> >
> >       pci_info(dev, "Intel SPT PCH root port ACS workaround enabled\n");
> > --
> > 2.27.0.212.ge8ba1cc988-goog
> >