linux-kernel - Re: [PATCH v2 3/6] iommufd: Initializing and releasing IO page fault data

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Message-ID: <276597d0-9947-44f1-a6b9-16d245394b22@linux.intel.com>
Date:   Wed, 13 Dec 2023 10:04:49 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...pe.ca>,
        Joel Granados <j.granados@...sung.com>
Cc:     baolu.lu@...ux.intel.com, Kevin Tian <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux.dev, linux-kselftest@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/6] iommufd: Initializing and releasing IO page fault
 data

On 12/12/23 10:12 PM, Jason Gunthorpe wrote:
> On Tue, Dec 12, 2023 at 02:10:08PM +0100, Joel Granados wrote:
> 
>>> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
>>> index 645ab5d290fe..0a8e03d5e7c5 100644
>>> --- a/drivers/iommu/iommufd/device.c
>>> +++ b/drivers/iommu/iommufd/device.c
>>> @@ -456,6 +456,16 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
>>>   	if (rc)
>>>   		goto err_unlock;
>>>   
>>> +	if (hwpt->fault) {
>>> +		void *curr;
>>> +
>>> +		curr = iopf_pasid_cookie_set(idev->dev, IOMMU_NO_PASID, idev);
>> I'm hitting an error here when I try to attach to a hwpt that I created
>> previously with the `IOMMU_HWPT_ALLOC_IOPF_CAPABLE` flag.
>>
>> I get an -ENODEV from iopf_pasid_cookie_set which is triggered by
>> dev->iommu->fault_param being 0x0.
>>
>> I looked around and I see that the fault param gets set in
>> iopf_queue_add_device which is called from iommu_dev_enable_feature
>> only. Furthermore iommu_dev_enable_feature is only called in idxd and
>> uacce drivers.
>>
>> Questions:
>> 1. Should iopf_queue_add_device get called from the
>>     IOMMU_HWPT_ALLOC_IOPF_CAPABLE ioctl call? This make sense to me as
>>     this is where the device and the IOPF are related from user space.
> It probably needs to call the set feature thing in the short term.
> 
> In the medium term I would like the drivers to manage the iopf based
> on domain attachment not explicit feature asks

Yes, it's the same as my plan.

> 
>> 2. This is not intended to work only with idxd and uacce. right?
> It should work everywhere, I suspect Intel Team didn't hit this
> because they are testing IDXD SIOV?

Yes.

> Can you guys also test it as a PF
> assignment?

For PF assignment, probably the driver (vfio-pci) needs to enable iopf.

Best regards,
baolu