On Sat, Jul 24, 2021 at 11:38:20PM +0200, Andreas Gruenbacher wrote: > Hmm, how could we have sub-page failure areas when this is about if > and how pages are mapped? If we return the number of bytes that are > accessible, then users will know if they got nothing, something, or > everything, and they can act accordingly. What I'm saying is that in situation when you have cacheline-sized poisoned areas, there's no way to get an accurate count of readable area other than try and copy it out. What's more, "something" is essentially useless information - the pages might get unmapped right as your function returns; the caller still needs to deal with partial copies. And that's a slow path by definition, so informing them of a partial fault-in is not going to be useful. As far as callers are concerned, it's "nothing suitable in the beginning of the area" vs. "something might be accessible".
