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

Lu Baolu
2020-01-18T02:06:29Z

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@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.
>

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

> Bjorn
>

Best regards,
baolu