On Wed, Jan 01, 2020 at 01:26:46PM +0800, Lu Baolu wrote:
> The new parameter takes a list of devices separated by a semicolon.
> Each device specified will have its iommu_passthrough bit in struct
> device set. This is very similar to the existing 'disable_acs_redir'
> parameter.
> 
> Signed-off-by: Lu Baolu <[email protected]>
> ---
>  .../admin-guide/kernel-parameters.txt         |  5 +++
>  drivers/pci/pci.c                             | 34 +++++++++++++++++++
>  drivers/pci/pci.h                             |  1 +
>  drivers/pci/probe.c                           |  2 ++
>  4 files changed, 42 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt 
> b/Documentation/admin-guide/kernel-parameters.txt
> index ade4e6ec23e0..d3edc2cb6696 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3583,6 +3583,11 @@
>                               may put more devices in an IOMMU group.
>               force_floating  [S390] Force usage of floating interrupts.
>               nomio           [S390] Do not use MIO instructions.
> +             iommu_passthrough=<pci_dev>[; ...]
> +                             Specify one or more PCI devices (in the format
> +                             specified above) separated by semicolons.
> +                             Each device specified will bypass IOMMU DMA
> +                             translation.
>  
>       pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State 
> Power
>                       Management.
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 90dbd7c70371..05bf3f4acc36 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6401,6 +6401,37 @@ void __weak pci_fixup_cardbus(struct pci_bus *bus)
>  }
>  EXPORT_SYMBOL(pci_fixup_cardbus);
>  
> +static const char *iommu_passthrough_param;
> +bool pci_iommu_passthrough_match(struct pci_dev *dev)
> +{
> +     int ret = 0;
> +     const char *p = iommu_passthrough_param;
> +
> +     if (!p)
> +             return false;
> +
> +     while (*p) {
> +             ret = pci_dev_str_match(dev, p, &p);
> +             if (ret < 0) {
> +                     pr_info_once("PCI: Can't parse iommu_passthrough 
> parameter: %s\n",
> +                                  iommu_passthrough_param);
> +
> +                     break;
> +             } else if (ret == 1) {
> +                     pci_info(dev, "PCI: IOMMU passthrough\n");
> +                     return true;
> +             }
> +
> +             if (*p != ';' && *p != ',') {
> +                     /* End of param or invalid format */
> +                     break;
> +             }
> +             p++;
> +     }
> +
> +     return false;
> +}

This duplicates a lot of the code in pci_disable_acs_redir().  That
needs to be factored out somehow so we don't duplicate it.

Bjorn
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