Re: [PATCH 1/2] vtd: Drop dead check for permissions in lookup_page

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Le 16/04/2026 à 10:23, Jan Beulich a écrit :
> On 10.04.2026 12:09, Teddy Astie wrote:
>> `val` comes from `addr_to_dma_page_maddr()` which is a pagetable
>> paddr and doesn't leak the PTE flags in it.
>
> Did you read the comment ahead of the function, in particular the part about
> the caller passing 0 for "target"?
>

Ah ok, the "full PTE contents below PADDR_BITS limit" also includes the
R/W flags, but only in that case.

While I'm on it, there is a corner case here where "full PTE content" is
also at the same time a error condition of this function (if PTE mfn ==
0, we have val < PAGE_SIZE; yet the mapping exists), but that's not the
problem this patch is fixing.

>> Rather than returning entries without any permissions, assume they
>> are always r/w.
>
> This wouldn't be any better.
>

Not having any permission could confuse the caller that there are no
mappings. But it depends mostly on the callers which don't exist yet.

> Jan
>

Teddy


--
Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech