Re: [PATCH -next] powerpc/mm: check base flags in ioremap_prot

Nanyong Sun [off-list ref] writes:

On 2021/9/3 17:16, Christophe Leroy wrote:

quoted

Le 03/09/2021 à 11:03, Nanyong Sun a écrit :

quoted

Some drivers who call ioremap_prot without setting base flags like
ioremap_prot(addr, len, 0) may work well before
commit 56f3c1413f5c ("powerpc/mm: properly set PAGE_KERNEL flags in
ioremap()"), but now they will get a virtual address "successfully"
from ioremap_prot and badly fault on memory access later because that
patch also dropped the hack adding of base flags for ioremap_prot.

So return NULL and throw a warning if the caller of ioremap_prot did
not set base flags properly. Why not just hack adding PAGE_KERNEL flags
in the ioremap_prot, because most scenarios can be covered by high level
functions like ioremap(), ioremap_coherent(), ioremap_cache()...
so it is better to keep max flexibility for this low level api.

As far as I can see, there is no user of this fonction that sets flags 
to 0 in the kernel tree.

Did you find any ? If you did, I think it is better to fix the caller.

Christophe

I see some vendor's drivers which are not on upstream ...

Sorry, but we don't carry extraneous checks in upstream for the sake of
out-of-tree drivers.

cheers