linux-kernel - Re: [PATCH v3 02/16] iommu: Introduce cache

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Message-ID: <20190513151637.79c273e2@jacob-builder>
Date:   Mon, 13 May 2019 15:16:37 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>
Cc:     Auger Eric <eric.auger@...hat.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v3 02/16] iommu: Introduce cache_invalidate API

On Mon, 13 May 2019 18:09:48 +0100
Jean-Philippe Brucker <jean-philippe.brucker@....com> wrote:

> On 13/05/2019 17:50, Auger Eric wrote:
> >> struct iommu_inv_pasid_info {
> >> #define IOMMU_INV_PASID_FLAGS_PASID	(1 << 0)
> >> #define IOMMU_INV_PASID_FLAGS_ARCHID	(1 << 1)
> >> 	__u32	flags;
> >> 	__u32	archid;
> >> 	__u64	pasid;
> >> };  
> > I agree it does the job now. However it looks a bit strange to do a
> > PASID based invalidation in my case - SMMUv3 nested stage - where I
> > don't have any PASID involved.
> > 
> > Couldn't we call it context based invalidation then? A context can
> > be tagged by a PASID or/and an ARCHID.  
> 
> I think calling it "context" would be confusing as well (I shouldn't
> have used it earlier), since VT-d uses that name for device table
> entries (=STE on Arm SMMU). Maybe "addr_space"?
> 
I am still struggling to understand what ARCHID is after scanning
through SMMUv3.1 spec. It seems to be a constant for a given SMMU. Why
do you need to pass it down every time? Could you point to me the
document or explain a little more on ARCHID use cases.
We have three fileds called pasid under this struct
iommu_cache_invalidate_info{}
Gets confusing :)
> Thanks,
> Jean
> 
> > 
> > Domain invalidation would invalidate all the contexts belonging to
> > that domain.
> > 
> > Thanks
> > 
> > Eric  

[Jacob Pan]