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 10:07 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
>
> Nit: Reorder these as in c8de8ed2dcaa ("PCI: Make ACS quirk
> implementations more uniform") so they match other similar lists in
> the code.

Will do.

>
> But more to the point: we have a bunch of other quirks for devices
> that do not have an ACS capability but *do* provide some ACS-like
> features.  Most of them support
>
>   PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF
>
> because that's what we usually want.  But I bet some of them also
> actually provide the equivalent of PCI_ACS_TB.
>
> REQ_ACS_FLAGS doesn't include PCI_ACS_TB.  Is there anything we need
> to do on the pci_acs_enabled() side to check for PCI_ACS_TB, and
> consequently, to update any of the quirks for devices that provide it?

I'm actually not sure.
+Alex Williamson , do you have any comments here?

Thanks,

Rajat

>
> > + *
> > + * Currently missing, it also needs to do equivalent of PCI_ACS_TB,
> > + * if dev->external_facing || dev->untrusted
> > + */
> >  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
> >