linux-kernel - Re: [PATCH v6 3/4] iommu/vt-d: Add set_dev

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Date:   Tue, 30 May 2023 13:55:21 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Joerg Roedel <joro@...tes.org>, dmaengine@...r.kernel.org,
        vkoul@...nel.org, Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>,
        narayan.ranganathan@...el.com
Subject: Re: [PATCH v6 3/4] iommu/vt-d: Add set_dev_pasid callback for dma
 domain

On Tue, May 30, 2023 at 10:19:05AM +0800, Baolu Lu wrote:
> On 5/30/23 3:48 AM, Jason Gunthorpe wrote:
> > On Fri, May 19, 2023 at 01:32:22PM -0700, Jacob Pan wrote:
> > 
> > > @@ -4720,25 +4762,99 @@ static void intel_iommu_iotlb_sync_map(struct iommu_domain *domain,
> > >   static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
> > >   {
> > >   	struct intel_iommu *iommu = device_to_iommu(dev, NULL, NULL);
> > > +	struct dev_pasid_info *curr, *dev_pasid = NULL;
> > > +	struct dmar_domain *dmar_domain;
> > >   	struct iommu_domain *domain;
> > > +	unsigned long flags;
> > > -	/* Domain type specific cleanup: */
> > >   	domain = iommu_get_domain_for_dev_pasid(dev, pasid, 0);
> > > -	if (domain) {
> > > -		switch (domain->type) {
> > > -		case IOMMU_DOMAIN_SVA:
> > > -			intel_svm_remove_dev_pasid(dev, pasid);
> > > -			break;
> > > -		default:
> > > -			/* should never reach here */
> > > -			WARN_ON(1);
> > > +	if (!domain)
> > > +		goto out_tear_down;
> > > +
> > > +	/*
> > > +	 * The SVA implementation needs to stop mm notification, drain the
> > > +	 * pending page fault requests before tearing down the pasid entry.
> > > +	 * The VT-d spec (section 6.2.3.1) also recommends that software
> > > +	 * could use a reserved domain id for all first-only and pass-through
> > > +	 * translations. Hence there's no need to call domain_detach_iommu()
> > > +	 * in the sva domain case.
> > > +	 */
> > > +	if (domain->type == IOMMU_DOMAIN_SVA) {
> > > +		intel_svm_remove_dev_pasid(dev, pasid);
> > > +		goto out_tear_down;
> > > +	}
> > 
> > But why don't you need to do all the other
> > intel_pasid_tear_down_entry(), intel_svm_drain_prq() (which is
> > misnamed) and other stuff from intel_svm_remove_dev_pasid() ?
> 
> Perhaps,
> 
> 	if (domain->type == IOMMU_DOMAIN_SVA) {
> 		intel_svm_remove_dev_pasid(dev, pasid);
> 		return;
> 	}
> 
> ?

I would expect only stuff directly connected to SVM be in the SVM
function.

De-initalizing PRI and any other pasid destruction should be in this
function.

> > There still seems to be waaay too much "SVM" in the PASID code.
> 
> This segment of code is destined to be temporary. From a long-term
> perspective, I hope to move SVA specific staffs such as mm notification,
> prq draining, etc. to the iommu core. They are generic rather than Intel
> iommu specific.

Yes, sort of, but.. That is just the mmu notifier bits

All the PRI/PASID teardown needs to be unlinked from SVM

> > It would be nice if the different domain types had their own ops..
> 
> Good suggestion!
> 
> We can add a domain ops in the Intel domain structure which is
> responsible for how to install an Intel iommu domain onto the VT-d
> hardware.

We should have seperate iommu_domain_ops at least, I think that would
cover alot of it?

Jason