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Date:   Mon, 6 Jul 2020 11:45:14 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Rajat Jain <rajatja@google.com>
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-acpi@vger.kernel.org, Raj Ashok <ashok.raj@intel.com>,
        lalithambika.krishnakumar@intel.com,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Prashant Malani <pmalani@google.com>,
        Benson Leung <bleung@google.com>,
        Todd Broch <tbroch@google.com>,
        Alex Levin <levinale@google.com>,
        Mattias Nissler <mnissler@google.com>,
        Rajat Jain <rajatxjain@gmail.com>,
        Bernie Keany <bernie.keany@intel.com>,
        Aaron Durbin <adurbin@google.com>,
        Diego Rivas <diegorivas@google.com>,
        Duncan Laurie <dlaurie@google.com>,
        Furquan Shaikh <furquan@google.com>,
        Jesse Barnes <jsbarnes@google.com>,
        Christian Kellner <christian@kellner.me>,
        Alex Williamson <alex.williamson@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        oohall@gmail.com, Saravana Kannan <saravanak@google.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
Subject: Re: [PATCH v2 3/7] PCI/ACS: Enable PCI_ACS_TB for
 untrusted/external-facing devices
Message-ID: <20200706164514.GA124720@bjorn-Precision-5520>
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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?

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
>