RE: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group

From: Tian, Kevin
Sent: Thursday, September 8, 2022 5:31 PM

quoted

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.

btw I saw the policy for -EBUSY is also not consistent in this series.

while it's correct to change -EBUSY to -EMEDIUMTYPE for omap, assuming
that retrying another fresh domain for the said device should work:

	if (omap_domain->dev) {
-		dev_err(dev, "iommu domain is already attached\n");
-		ret = -EBUSY;
+		ret = -EMEDIUMTYPE;
 		goto out;
 	}

the change in tegra-gart doesn't sound correct:

	if (gart->active_domain && gart->active_domain != domain) {
-		ret = -EBUSY;
+		ret = -EMEDIUMTYPE;

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.

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.
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