linux-kernel - Re: [PATCH 5/6] iommu: init pasid array while doing domain

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Message-ID: <b7a68539-3a3c-4cd9-922b-bfb9db8e7e0b@linux.intel.com>
Date: Thu, 12 Sep 2024 12:21:53 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Joel Granados <j.granados@...sung.com>
Cc: baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>, Jason Gunthorpe <jgg@...pe.ca>,
 Kevin Tian <kevin.tian@...el.com>, Klaus Jensen <its@...elevant.dk>,
 linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Subject: Re: [PATCH 5/6] iommu: init pasid array while doing domain_replace
 and iopf is active

On 9/11/24 6:56 PM, Joel Granados wrote:
> On Thu, Sep 05, 2024 at 11:30:05AM +0800, Baolu Lu wrote:
>> On 9/4/24 9:17 PM, Joel Granados via B4 Relay wrote:
>>> From: Joel Granados<j.granados@...sung.com>
>>>
>>> iommu_report_device_fault expects a pasid array to have an
>>> iommu_attach_handle when a fault is detected.
>> The iommu_attach_handle is expected only when an iopf-capable domain is
>> attached to the device or PASID. The iommu_report_device_fault() treats
>> it as a fault when a fault occurs, but no iopf-capable domain is
>> attached.
>>
>>> Add this handle when the
>>> replacing hwpt has a valid iommufd fault object. Remove it when we
>>> release ownership of the group.
>> The iommu_attach_handle is managed by the caller (iommufd here for
>> example). Therefore, before iommu_attach_handle tries to attach a domain
>> to an iopf-capable device or pasid, it should allocate the handle and
>> pass it to the domain attachment interfaces.
> What do you mean here?
> 1. Do you want to move the iommufd_init_pasid_array call up to
> iommufd_hwpt_replace_device?
> 2. Do you want to move it further up to iommufd_device_do_replace?

I'm having trouble understanding the need for iommu_init_pasid_array()
in the core.

> 
> Note that all this implemented on a call to replace HWPT. So a
> non-iopf-capable VFIO_DEVICE_ATTACH_IOMMUFD_PT ioctl has already been
> completed before the one that calls iommufd_device_do_replace.
> 
>> Conversely, the handle can
>> only be freed after the domain is detached.
> Do you have a function in specific where you would put the free handle
> logic?

drivers/iommu/iommufd/fault.c

void iommufd_fault_domain_detach_dev(struct iommufd_hw_pagetable *hwpt,
                                      struct iommufd_device *idev)
{
         struct iommufd_attach_handle *handle;

         handle = iommufd_device_get_attach_handle(idev);
         iommu_detach_group_handle(hwpt->domain, idev->igroup->group);
         iommufd_auto_response_faults(hwpt, handle);
         iommufd_fault_iopf_disable(idev);
         kfree(handle);
}

Thanks,
baolu