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

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Message-ID: <20240912100058.gnu2bzytexhdfq7e@joelS2.panther.com>
Date: Thu, 12 Sep 2024 12:00:58 +0200
From: Joel Granados <j.granados@...sung.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>
CC: 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 Thu, Sep 12, 2024 at 12:21:53PM +0800, Baolu Lu wrote:
> 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);
> }
Actually there is no need to add the xa_erase call in
__iommu_release_dma_ownership because it is *already* handled here.
Sorry about this, I think this was left from a previous version of the
patch. I'll remove the superfluous xa_erase call.

Thx for the review

-- 

Joel Granados