Re: [PATCH v4 3/6] iommu/vt-d: Implement domain ops for attach_dev_pasid

From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: vkoul@kernel.org, "Tian, Kevin" <kevin.tian@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	will@kernel.org, David Woodhouse <dwmw2@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	iommu@lists.linux-foundation.org, dmaengine@vger.kernel.org,
	robin.murphy@arm.com,
	Jean-Philippe Brucker <jean-philippe@linaro.com>
Subject: Re: [PATCH v4 3/6] iommu/vt-d: Implement domain ops for attach_dev_pasid
Date: Tue, 24 May 2022 09:12:35 -0700	[thread overview]
Message-ID: <20220524091235.6dddfab4@jacob-builder> (raw)
In-Reply-To: <20220524135135.GV1343366@nvidia.com>

Hi Jason,

On Tue, 24 May 2022 10:51:35 -0300, Jason Gunthorpe <jgg@nvidia.com> wrote:

> On Wed, May 18, 2022 at 11:21:17AM -0700, Jacob Pan wrote:
> > On VT-d platforms with scalable mode enabled, devices issue DMA requests
> > with PASID need to attach PASIDs to given IOMMU domains. The attach
> > operation involves the following:
> > - Programming the PASID into the device's PASID table
> > - Tracking device domain and the PASID relationship
> > - Managing IOTLB and device TLB invalidations
> > 
> > This patch add attach_dev_pasid functions to the default domain ops
> > which is used by DMA and identity domain types. It could be extended to
> > support other domain types whenever necessary.
> > 
> > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> >  drivers/iommu/intel/iommu.c | 72 +++++++++++++++++++++++++++++++++++--
> >  1 file changed, 70 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 1c2c92b657c7..75615c105fdf 100644
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -1556,12 +1556,18 @@ static void __iommu_flush_dev_iotlb(struct
> > device_domain_info *info, u64 addr, unsigned int mask)
> >  {
> >  	u16 sid, qdep;
> > +	ioasid_t pasid;
> >  
> >  	if (!info || !info->ats_enabled)
> >  		return;
> >  
> >  	sid = info->bus << 8 | info->devfn;
> >  	qdep = info->ats_qdep;
> > +	pasid = iommu_get_pasid_from_domain(info->dev,
> > &info->domain->domain);  
> 
> No, a simgple domain can be attached to multiple pasids, all need to
> be flushed.
> 
Here is device TLB flush, why would I want to flush PASIDs other than my
own device attached?

At one level up, we do have a list of device to be flushed.
	list_for_each_entry(info, &domain->devices, link)
		__iommu_flush_dev_iotlb(info, addr, mask);

Note that RID2PASID is not in the pasid_array, its DEVTLB flush also needs
special handling in that the device is doing DMA w/o PASID, thus not aware
of RID2PASID.

> This whole API isn't suitable.
> 
> Jason

Thanks,

Jacob
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