From: Jason Gunthorpe <jgg@nvidia.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: iommu@lists.linux-foundation.org,
LKML <linux-kernel@vger.kernel.org>,
dmaengine@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
David Woodhouse <dwmw2@infradead.org>,
Jean-Philippe Brucker <jean-philippe@linaro.com>,
Lu Baolu <baolu.lu@linux.intel.com>,
Christoph Hellwig <hch@infradead.org>,
vkoul@kernel.org, robin.murphy@arm.com, will@kernel.org,
Yi Liu <yi.l.liu@intel.com>, Dave Jiang <dave.jiang@intel.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
Raj Ashok <ashok.raj@intel.com>,
Eric Auger <eric.auger@redhat.com>
Subject: Re: [PATCH v4 1/6] iommu: Add a per domain PASID for DMA API
Date: Mon, 30 May 2022 09:22:47 -0300 [thread overview]
Message-ID: <20220530122247.GY1343366@nvidia.com> (raw)
In-Reply-To: <20220524081727.19c2dd6d@jacob-builder>
On Tue, May 24, 2022 at 08:17:27AM -0700, Jacob Pan wrote:
> Hi Jason,
>
> On Tue, 24 May 2022 10:50:34 -0300, Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> > On Wed, May 18, 2022 at 11:21:15AM -0700, Jacob Pan wrote:
> > > DMA requests tagged with PASID can target individual IOMMU domains.
> > > Introduce a domain-wide PASID for DMA API, it will be used on the same
> > > mapping as legacy DMA without PASID. Let it be IOVA or PA in case of
> > > identity domain.
> >
> > Huh? I can't understand what this is trying to say or why this patch
> > makes sense.
> >
> > We really should not have pasid's like this attached to the domains..
> >
> This is the same "DMA API global PASID" you reviewed in v3, I just
> singled it out as a standalone patch and renamed it. Here is your previous
> review comment.
>
> > +++ b/include/linux/iommu.h
> > @@ -105,6 +105,8 @@ struct iommu_domain {
> > enum iommu_page_response_code (*iopf_handler)(struct iommu_fault *fault,
> > void *data);
> > void *fault_data;
> > + ioasid_t pasid; /* Used for DMA requests with PASID */
> > + atomic_t pasid_users;
>
> These are poorly named, this is really the DMA API global PASID and
> shouldn't be used for other things.
>
>
>
> Perhaps I misunderstood, do you mind explaining more?
You still haven't really explained what this is for in this patch,
maybe it just needs a better commit message, or maybe something is
wrong.
I keep saying the DMA API usage is not special, so why do we need to
create a new global pasid and refcount? Realistically this is only
going to be used by IDXD, why can't we just allocate a PASID and
return it to the driver every time a driver asks for DMA API on PASI
mode? Why does the core need to do anything special?
Jason
next prev parent reply other threads:[~2022-05-30 12:22 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-18 18:21 [PATCH v4 0/6] Enable PASID for DMA API users Jacob Pan
2022-05-18 18:21 ` [PATCH v4 1/6] iommu: Add a per domain PASID for DMA API Jacob Pan
2022-05-19 6:50 ` Baolu Lu
2022-05-24 13:50 ` Jason Gunthorpe
2022-05-24 15:17 ` Jacob Pan
2022-05-30 12:22 ` Jason Gunthorpe [this message]
2022-05-31 10:12 ` Tian, Kevin
2022-05-31 12:45 ` Baolu Lu
2022-05-31 16:03 ` Jason Gunthorpe
2022-05-31 17:29 ` Jacob Pan
2022-05-31 19:05 ` Jason Gunthorpe
2022-05-31 20:44 ` Jacob Pan
2022-06-01 1:50 ` Tian, Kevin
2022-06-01 1:43 ` Tian, Kevin
2022-06-01 9:37 ` Baolu Lu
2022-06-01 10:05 ` Tian, Kevin
2022-05-18 18:21 ` [PATCH v4 2/6] iommu: Add a helper to do PASID lookup from domain Jacob Pan
2022-05-19 6:41 ` Baolu Lu
2022-05-19 20:10 ` Jacob Pan
2022-05-19 6:48 ` Christoph Hellwig
2022-05-20 15:18 ` Jacob Pan
2022-05-23 7:55 ` Tian, Kevin
2022-05-23 9:14 ` Tian, Kevin
2022-05-23 18:01 ` Jacob Pan
2022-05-18 18:21 ` [PATCH v4 3/6] iommu/vt-d: Implement domain ops for attach_dev_pasid Jacob Pan
2022-05-24 13:51 ` Jason Gunthorpe
2022-05-24 16:12 ` Jacob Pan
2022-05-24 18:02 ` Jason Gunthorpe
2022-05-24 20:45 ` Jacob Pan
2022-05-24 21:10 ` Jason Gunthorpe
2022-05-18 18:21 ` [PATCH v4 4/6] iommu: Add PASID support for DMA mapping API users Jacob Pan
2022-05-23 8:25 ` Tian, Kevin
2022-05-23 15:23 ` Jacob Pan
2022-05-18 18:21 ` [PATCH v4 5/6] dmaengine: idxd: Use DMA API for in-kernel DMA with PASID Jacob Pan
2022-05-18 18:21 ` [PATCH v4 6/6] iommu/vt-d: Delete unused SVM flag Jacob Pan
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