Re: [PATCH v2 4/7] iommu: Let iommu.strict override ops->def_domain_type

From: Jason Gunthorpe <jgg@nvidia.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>,
	Baolu Lu <baolu.lu@linux.intel.com>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Gerd Bayer <gbayer@linux.ibm.com>,
	iommu@lists.linux.dev, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>,
	Wenjia Zhang <wenjia@linux.ibm.com>,
	Pierre Morel <pmorel@linux.ibm.com>,
	linux-s390@vger.kernel.org, borntraeger@linux.ibm.com,
	hca@linux.ibm.com, gor@linux.ibm.com,
	gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com,
	svens@linux.ibm.com, linux-kernel@vger.kernel.org,
	Julian Ruess <julianr@linux.ibm.com>
Subject: Re: [PATCH v2 4/7] iommu: Let iommu.strict override ops->def_domain_type
Date: Tue, 29 Nov 2022 13:33:10 -0400	[thread overview]
Message-ID: <Y4ZCVgLO9AHatwXe@nvidia.com> (raw)
In-Reply-To: <6c4c3a3e-1d8d-7994-3c03-388ef63dddb3@arm.com>

On Mon, Nov 28, 2022 at 09:01:43PM +0000, Robin Murphy wrote:

> I'm hardly an advocate for trying to save users from themselves, but I
> honestly can't see any justifiable reason for not having sysfs respect
> iommu_get_def_domain_type(). 

We really need to rename this value if it is not actually just an
advisory "default" but a functional requirement ..

> > The driver should have no say in how dma-iommu.c works beyond if it
> > provides the required ops functionalities, and hint(s) as to what
> > gives best performance.
> 
> That should already be the case today, as outlined in my other mail. It's
> just somewhat more evolved than designed, so may not be so clear to
> everyone.

It is close to being clear, once we get the last touches of dma-iommu
stuff out of the drivers it should be quite clear

Thanks,
Jason