Re: [RFC 16/26] memory: Make flatview_do_translate() return a pointer to MemoryRegionSection

[Zhao Liu <zhao1.liu@intel.com>]

On Tue, Aug 12, 2025 at 09:23:59PM +0200, Paolo Bonzini wrote:
> Date: Tue, 12 Aug 2025 21:23:59 +0200
> From: Paolo Bonzini <pbonzini@redhat.com>
> Subject: Re: [RFC 16/26] memory: Make flatview_do_translate() return a
>  pointer to MemoryRegionSection
> 
> Il mar 12 ago 2025, 17:17 Zhao Liu <zhao1.liu@intel.com> ha scritto:
> 
> > But look closer to Opaque<>, it has 2 safe methods: as_mut_ptr() &
> > raw_get().
> >
> > These 2 methods indicate that the T pointed by Qpaque<T> is mutable,
> > which has the conflict with the original `*const
> > bindings::MemoryRegionSection`.
> >
> > So from this point, it seems unsafe to use Qpaque<> on this case.
> >
> 
> Yes, it's similar to NonNull<>. I am not sure that you need Opaque<> here;
> since the pointer is const, maybe you can just dereference it to a
> &bindings::MemoryRegionSection. Is it useful to have the Opaque<> wrapper
> here?

I agree. Opaque<> is not necessary here. We can have a simple wrapper:

pub struct MemoryRegionSection(*const bindings::MemoryRegionSection)

or

pub struct MemoryRegionSection(NonNull<bindings::MemoryRegionSection>)
with immutable only use.

In future, if there're more similar case, then we can have a OpaqueRef<>
like Manos suggested.

Thanks,
Zhao