linux-kernel - RE: [PATCH v2 2/5] iommu: Introduce mm_get

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Message-ID: <MW5PR11MB5881784C1598B32CE8A0D7E489E4A@MW5PR11MB5881.namprd11.prod.outlook.com>
Date:   Fri, 1 Sep 2023 03:29:10 +0000
From:   "Zhang, Tina" <tina.zhang@...el.com>
To:     Jason Gunthorpe <jgg@...pe.ca>, Baolu Lu <baolu.lu@...ux.intel.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        Michael Shavit <mshavit@...gle.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/5] iommu: Introduce mm_get_pasid() helper function

Hi Baolu and Jason,

> -----Original Message-----
> From: Jason Gunthorpe <jgg@...pe.ca>
> Sent: Friday, September 1, 2023 1:03 AM
> To: Baolu Lu <baolu.lu@...ux.intel.com>
> Cc: Zhang, Tina <tina.zhang@...el.com>; Tian, Kevin <kevin.tian@...el.com>;
> Michael Shavit <mshavit@...gle.com>; iommu@...ts.linux.dev; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH v2 2/5] iommu: Introduce mm_get_pasid() helper function
> 
> On Thu, Aug 31, 2023 at 01:14:20PM +0800, Baolu Lu wrote:
> > On 2023/8/27 16:43, Tina Zhang wrote:
> > > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > > index e95b339e9cdc0..e6377cff6a935 100644
> > > --- a/drivers/iommu/intel/svm.c
> > > +++ b/drivers/iommu/intel/svm.c
> > > @@ -306,13 +306,13 @@ static int intel_svm_bind_mm(struct intel_iommu
> *iommu, struct device *dev,
> > >   	unsigned long sflags;
> > >   	int ret = 0;
> > > -	svm = pasid_private_find(mm->pasid);
> > > +	svm = pasid_private_find(mm_get_pasid(mm));
> > >   	if (!svm) {
> > >   		svm = kzalloc(sizeof(*svm), GFP_KERNEL);
> > >   		if (!svm)
> > >   			return -ENOMEM;
> > > -		svm->pasid = mm->pasid;
> > > +		svm->pasid = mm_get_pasid(mm);
> > >   		svm->mm = mm;
> > >   		INIT_LIST_HEAD_RCU(&svm->devs);
> > > @@ -350,7 +350,7 @@ static int intel_svm_bind_mm(struct intel_iommu
> *iommu, struct device *dev,
> > >   	/* Setup the pasid table: */
> > >   	sflags = cpu_feature_enabled(X86_FEATURE_LA57) ?
> PASID_FLAG_FL5LP : 0;
> > > -	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, mm->pasid,
> > > +	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd,
> > > +mm_get_pasid(mm),
> > >   					    FLPT_DEFAULT_DID, sflags);
> > >   	if (ret)
> > >   		goto free_sdev;
> > > @@ -364,7 +364,7 @@ static int intel_svm_bind_mm(struct intel_iommu
> *iommu, struct device *dev,
> > >   free_svm:
> > >   	if (list_empty(&svm->devs)) {
> > >   		mmu_notifier_unregister(&svm->notifier, mm);
> > > -		pasid_private_remove(mm->pasid);
> > > +		pasid_private_remove(mm_get_pasid(mm));
> > >   		kfree(svm);
> > >   	}
> >
> > There is no need to use mm_get_pasid(mm) in the set_dev_pasid path.
> > The pasid has already passed as a parameter. Perhaps, pass domain and
> > pasid to intel_svm_bind_mm(), or simply merge intel_svm_bind_mm() to
> > intel_svm_set_dev_pasid()?
> >
> > Something like below?
> 
> Yes please! As a prep patch 'remove mm->pasid references from vt-d'

Reasonable, as we believe that eventually vt-d driver only needs mm->pgd, nothing else for mm.

Thanks,
-Tina
> 
> Jason