Re: [RFC PATCH 2/4] PCI: Add "pci=iommu_passthrough=" parameter for iommu passthrough

Bjorn Helgaas
2020-01-18T00:18:54Z

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 <baolu.lu@linux.intel.com>
> ---
> .../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