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

[Lu Baolu]

Hi Bjorn,

On 1/18/20 8:18 AM, Bjorn Helgaas wrote:
> 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@xxxxxxxxxxxxxxx>
> > ---
> >   .../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.

Sure. I will try to refactor the code in the next version.

> Bjorn

Best regards,
baolu