linux-kernel - RE: [PATCH v7 4/5] iommu: Support mm PASID 1:n with sva domains

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Message-ID: <MW5PR11MB5881ECF6757B0211A18B208C89D2A@MW5PR11MB5881.namprd11.prod.outlook.com>
Date:   Fri, 13 Oct 2023 09:57:30 +0000
From:   "Zhang, Tina" <tina.zhang@...el.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Michael Shavit <mshavit@...gle.com>,
        Vasant Hegde <vasant.hegde@....com>,
        Nicolin Chen <nicolinc@...dia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: RE: [PATCH v7 4/5] iommu: Support mm PASID 1:n with sva domains

Hi,

> -----Original Message-----
> From: Jason Gunthorpe <jgg@...pe.ca>
> Sent: Thursday, October 12, 2023 9:43 PM
> To: Zhang, Tina <tina.zhang@...el.com>
> Cc: Tian, Kevin <kevin.tian@...el.com>; Lu Baolu <baolu.lu@...ux.intel.com>;
> Michael Shavit <mshavit@...gle.com>; Vasant Hegde
> <vasant.hegde@....com>; Nicolin Chen ^C-cc=iommu @ lists . linux . dev
> <nicolinc@...dia.com>; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v7 4/5] iommu: Support mm PASID 1:n with sva domains
> 
> On Thu, Oct 12, 2023 at 11:01:11AM +0800, Tina Zhang wrote:
> 
> > @@ -1188,15 +1193,26 @@ static inline bool
> > tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream  #ifdef
> > CONFIG_IOMMU_SVA  static inline void mm_pasid_init(struct mm_struct
> > *mm)  {
> > -	mm->pasid = IOMMU_PASID_INVALID;
> > +	/*
> > +	 * During dup_mm(), a new mm will be memcpy'd from an old one
> and that makes
> > +	 * the new mm and the old one point to a same iommu_mm
> instance. When either
> > +	 * one of the two mms gets released, the iommu_mm instance is
> freed, leaving
> > +	 * the other mm running into a use-after-free/double-free problem.
> To avoid
> > +	 * the problem, zeroing the iommu_mm pointer of a new mm is
> needed here.
> > +	 */
> > +	mm->iommu_mm = NULL;
> >  }
> 
> newlines after all the }, between functions doesn't checkpatch complain?
Checked with checkpatch but didn't see any complaining.

> 
> IMHO this hunk should be moved to the prior patch.
In this patch, we switch to use mm->iommu_mm. That's why the iommu_mm initialization is put in this patch.

I think I met some problem about my mailbox when I was sending this new version. It didn't cc iommu@...ts.linux.dev. Should I resend this version again or reply to the patches with iommu@...ts.linux.dev cc'd?

Regards,
-Tina
> 
> But it all looks good to me now
> 
> Thanks,
> Jason