linux-kernel - Re: [PATCH 2/4] iommu/vt-d: Use non-privileged mode for all PASIDs

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Date:   Fri, 3 Mar 2023 13:40:09 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Jason Gunthorpe <jgg@...dia.com>,
        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>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 2/4] iommu/vt-d: Use non-privileged mode for all PASIDs

Hi Baolu,

On Thu, 2 Mar 2023 22:11:36 +0800, Baolu Lu <baolu.lu@...ux.intel.com>
wrote:

> On 2023/3/2 8:59, Jacob Pan wrote:
> > For in-kernel DMA, use non-privileged access for all PASIDs to be
> > consistent with RID_PASID.
> > There's no need to differentiate user and kernel for in-kernel DMA. >
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > ---
> >   drivers/iommu/intel/iommu.c | 2 --
> >   1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index a0cb3bc851ac..9e3c056e392d 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -2334,8 +2334,6 @@ static int domain_setup_first_level(struct
> > intel_iommu *iommu, if (level != 4 && level != 5)
> >   		return -EINVAL;
> >   
> > -	if (pasid != PASID_RID2PASID)
> > -		flags |= PASID_FLAG_SUPERVISOR_MODE;  
> 
> With above removed, PASID_FLAG_SUPERVISOR_MODE is not used anywhere?
> Perhaps you can cleanup it to avoid dead code?
good point, we could remove pasid_set_sre() related code for FL,SL, and PT.

Thanks,

Jacob