linux-kernel - RE: [PATCH v3 5/6] iommu: Use EINVAL for incompatible device/domain in ->attach

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Message-ID: <BN9PR11MB5276378232A91ECEAEC4E2A68C4F9@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Wed, 21 Sep 2022 08:14:52 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Nicolin Chen <nicolinc@...dia.com>,
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Subject: RE: [PATCH v3 5/6] iommu: Use EINVAL for incompatible device/domain
 in ->attach_dev

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Wednesday, September 21, 2022 2:07 AM
> 
> On Tue, Sep 20, 2022 at 06:38:18AM +0000, Tian, Kevin wrote:
> 
> > Above lacks of a conversion in intel-iommu:
> >
> > intel_iommu_attach_device()
> > 	if (domain->type == IOMMU_DOMAIN_UNMANAGED &&
> > 	    device_is_rmrr_locked(dev)) {
> > 		dev_warn(dev, "Device is ineligible for IOMMU domain
> attach due to platform RMRR requirement.  Contact your platform
> vendor.\n");
> > 		return -EPERM;
> > 	}
> >
> > since it's based on the domain type, picking a different domain
> > may work in theory though it won't apply to vfio which always
> > creates unmanaged type.
> 
> IMHO this test shouldn't even be here, that is why it is so
> strange..
> 
> VFIO should be checking if somehow the device doesn't support
> unmanaged domains at all. We already have several drivers that can't
> support full featured unamanged domains that vfio needs, this is just
> another case of that.
> 
> But it isn't urgent to fix, I would just ignore this branch for this
> series.
> 

OK, then let's leave it as is. Anyway this is a rare path. In reality
most RMRR devices are gpu/usb which are already exempted
from the above check.