Re: [Xen-devel] [PATCH v5 14/18] x86/mem_sharing: use default_access in add_to_physmap

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Wed, Jan 22, 2020 at 8:35 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 21.01.2020 18:49, Tamas K Lengyel wrote:
> > When plugging a hole in the target physmap don't use the access permission
> > returned by __get_gfn_type_access as it can be non-sensical,
>
> "can be" is too vague for my taste - it suggests there may also be cases
> where a sensible value is returned, and hence it should be used. Could
> you clarify this please? (The code change itself of course is simple and
> mechanical enough to look okay.)

Well, I can only speak of what I observed. The case seems to be that
most of the time the function actually returns p2m_access_rwx (which
is sensible), but occasionally something else. I didn't investigate
where that value actually comes from, but when populating a physmap
like this only the default_access is sane.

Tamas

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