Re: Re: [PATCH v1 1/3] softmmu/physmem: fallback to opening guest RAM file as readonly in a MAP_PRIVATE mapping

[Peter Xu]

On Fri, Aug 11, 2023 at 01:06:12AM +0800, ThinerLogoer wrote:
> >I think we have the following options (there might be more)
> >
> >1) This patch.
> >
> >2) New flag for memory-backend-file. We already have "readonly" and 
> >"share=". I'm having a hard time coming up with a good name that really 
> >describes the subtle difference.
> >
> >3) Glue behavior to the QEMU machine
> >
> 
> 4) '-deny-private-discard' argv, or environment variable, or both

I'd personally vote for (2).  How about "fdperm"?  To describe when we want
to use different rw permissions on the file (besides the access permission
of the memory we already provided with "readonly"=XXX).  IIUC the only sane
value will be ro/rw/default, where "default" should just use the same rw
permission as the memory ("readonly"=XXX).

Would that be relatively clean and also work in this use case?

(the other thing I'd wish we don't have that fallback is, as long as we
 have any of that "fallback" we'll need to be compatible with it since
 then, and for ever...)

-- 
Peter Xu