On 2022/2/8 16:05, John Garry wrote:
> On 24/01/2022 13:11, Yicong Yang wrote:
>> The DMA of HiSilicon PTT device can only work with identical
>> mapping. So add a quirk for the device to force the domain
>> passthrough.
>
> This patch should be earlier in the series, before the PTT driver, and the comment on hisi_ptt_check_iommu_mapping() should mention what is going on here.
>
ok I'll reorder the serives and modify the comments of hisi_ptt_check_iommu_mapping() like:
/*
* The DMA of PTT trace can only use direct mapping, due to some
* hardware restriction. Check whether there is an iommu or the
* policy of the iommu domain is passthrough, otherwise the trace
* cannot work.
*
* The PTT device is supposed to behind the arm smmu v3, which
* should have passthrough the device by a quirk. Otherwise user
* should manually set the iommu domain type to identity through
* sysfs.
*/
>>
>> Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
>> ---
>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 6dc6d8b6b368..6f67a2b1dd27 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -2838,6 +2838,21 @@ static int arm_smmu_dev_disable_feature(struct device *dev,
>> }
>> }
>> +#define IS_HISI_PTT_DEVICE(pdev) ((pdev)->vendor == PCI_VENDOR_ID_HUAWEI && \
>> + (pdev)->device == 0xa12e)
>
> I assume that not all revisions will require this check, right?
>
For current revisions it's necessary.
>> +
>> +static int arm_smmu_def_domain_type(struct device *dev)
>> +{
>> + if (dev_is_pci(dev)) {
>> + struct pci_dev *pdev = to_pci_dev(dev);
>> +
>> + if (IS_HISI_PTT_DEVICE(pdev))
>> + return IOMMU_DOMAIN_IDENTITY;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> static struct iommu_ops arm_smmu_ops = {
>> .capable = arm_smmu_capable,
>> .domain_alloc = arm_smmu_domain_alloc,
>> @@ -2863,6 +2878,7 @@ static struct iommu_ops arm_smmu_ops = {
>> .sva_unbind = arm_smmu_sva_unbind,
>> .sva_get_pasid = arm_smmu_sva_get_pasid,
>> .page_response = arm_smmu_page_response,
>> + .def_domain_type = arm_smmu_def_domain_type,
>> .pgsize_bitmap = -1UL, /* Restricted during device attach */
>> .owner = THIS_MODULE,
>> };
>
> .
