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Subject: RE: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain
 and device/group
Thread-Topic: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible
 domain and device/group
Thread-Index: AQHYsNLwCXoHuSRk00qOEfaHbTrxlq3UDMUAgAASXoCAAAnsgIAALAkAgAAs1YCAAFRzgIAAh2pAgAARlrA=
Date:   Thu, 8 Sep 2022 09:54:18 +0000
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References: <20220815181437.28127-1-nicolinc@nvidia.com>
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> From: Tian, Kevin
> Sent: Thursday, September 8, 2022 5:31 PM
> > This mixture of error codes is the basic reason why a new code was
> > used, because none of the existing codes are used with any
> > consistency.
>=20
> btw I saw the policy for -EBUSY is also not consistent in this series.
>=20
> while it's correct to change -EBUSY to -EMEDIUMTYPE for omap, assuming
> that retrying another fresh domain for the said device should work:
>=20
> 	if (omap_domain->dev) {
> -		dev_err(dev, "iommu domain is already attached\n");
> -		ret =3D -EBUSY;
> +		ret =3D -EMEDIUMTYPE;
>  		goto out;
>  	}
>=20
> the change in tegra-gart doesn't sound correct:
>=20
> 	if (gart->active_domain && gart->active_domain !=3D domain) {
> -		ret =3D -EBUSY;
> +		ret =3D -EMEDIUMTYPE;
>=20
> one device cannot be attached to two domains. This fact doesn't change
> no matter how many domains are tried. In concept this check is
> redundant and should have been done by iommu core, but obviously we
> didn't pay attention to what -EBUSY actually represents in this path.
>=20

oops. Above is actually a right retry condition. gart is iommu instead of
device. So in concept retrying gart->active_domain for the device could
work.

So please ignore this comment.