linux-kernel - Re: [PATCH V2] PCI: add QCOM root port quirks for ACS

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Message-ID: <20170216151845.739c7336@t450s.home>
Date:   Thu, 16 Feb 2017 15:18:45 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     linux-pci@...r.kernel.org, timur@...eaurora.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH V2] PCI: add QCOM root port quirks for ACS

On Thu, 16 Feb 2017 17:01:45 -0500
Sinan Kaya <okaya@...eaurora.org> wrote:

> PCI Express defines an optional featured called Access Control Services
> described in 6.12. Access Control Services (ACS) section of the PCIe 3.1
> Specification.
> 
> Linux kernel uses ACS to validate/prohibit data transfers among PCIe
> functions. This becomes especially useful when running guest machines
> with PCI device passthrough. It provides security guarantee that only
> OS allowed PCIe devices can talk to each other.
> 
> QCOM root ports do provide ACS-like features to disable peer
> transactions and validate bus numbers in requests, but do not provide an
> actual PCIe ACS capability.
> 
> To be specific:
> * Hardware supports source validation but it will report the issue as
> Completer Abort instead of ACS Violation.
> 
> * Hardware doesn't support peer-to-peer and each root port is a root
> complex with unique segment numbers.
> 
> * It is not possible for one root port to pass traffic to the other root
> port. All PCIe transactions are terminated inside the root port.
> 
> Adding an ACS quirk for the QDF2400 and QDF2432 products.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---

Looks ok to me.  Thanks

Reviewed-by: Alex Williamson <alex.williamson@...hat.com>


>  drivers/pci/quirks.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 1800bef..2df06cb 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4136,6 +4136,27 @@ static int pci_quirk_intel_pch_acs(struct pci_dev *dev, u16 acs_flags)
>  }
>  
>  /*
> + * These QCOM root ports do provide ACS-like features to disable peer
> + * transactions and validate bus numbers in requests, but do not provide an
> + * actual PCIe ACS capability.
> + * Hardware supports source validation but it will report the issue as
> + * Completer Abort instead of ACS Violation.
> + * Hardware doesn't support peer-to-peer and each root port is a root complex
> + * with unique segment numbers.
> + * It is not possible for one root port to pass traffic to the other root
> + * port. All PCIe transactions are terminated inside the root port.
> + */
> +static int pci_quirk_qcom_rp_acs(struct pci_dev *dev, u16 acs_flags)
> +{
> +	u16 flags = (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF | PCI_ACS_SV);
> +	int ret = acs_flags & ~flags ? 0 : 1;
> +
> +	dev_info(&dev->dev, "Using QCOM ACS Quirk (%d)\n", ret);
> +
> +	return ret;
> +}
> +
> +/*
>   * Sunrise Point PCH root ports implement ACS, but unfortunately as shown in
>   * the datasheet (Intel 100 Series Chipset Family PCH Datasheet, Vol. 2,
>   * 12.1.46, 12.1.47)[1] this chipset uses dwords for the ACS capability and
> @@ -4271,6 +4292,9 @@ static int pci_quirk_mf_endpoint_acs(struct pci_dev *dev, u16 acs_flags)
>  	/* I219 */
>  	{ PCI_VENDOR_ID_INTEL, 0x15b7, pci_quirk_mf_endpoint_acs },
>  	{ PCI_VENDOR_ID_INTEL, 0x15b8, pci_quirk_mf_endpoint_acs },
> +	/* QCOM QDF2xxx root ports */
> +	{ 0x17CB, 0x400, pci_quirk_qcom_rp_acs },
> +	{ 0x17CB, 0x401, pci_quirk_qcom_rp_acs },
>  	/* Intel PCH root ports */
>  	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_intel_pch_acs },
>  	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_intel_spt_pch_acs },