Re: [PATCH 1/3] memory: add readonly support to memory_region_init_ram_from_file()

[Stefan Hajnoczi]

On Tue, Aug 04, 2020 at 02:26:22PM +0200, Philippe Mathieu-Daudé wrote:
> On 8/4/20 2:25 PM, Philippe Mathieu-Daudé wrote:
> > Hi Stefan,
> > 
> > On 8/4/20 12:12 PM, Stefan Hajnoczi wrote:
> >> There is currently no way to open(O_RDONLY) and mmap(PROT_READ) when
> >> creating a memory region from a file. This functionality is needed since
> >> the underlying host file may not allow writing.
> >>
> >> Add a bool readonly argument to memory_region_init_ram_from_file() and
> >> the APIs it calls.
> >>
> >> Extend memory_region_init_ram_from_file() rather than introducing a
> >> memory_region_init_rom_from_file() API so that callers can easily make a
> >> choice between read/write and read-only at runtime without calling
> >> different APIs.
> > 
> > What happens if we call:
> > 
> >  memory_region_init_ram_from_file(mr, ..., readonly=false, ...);
> >  memory_region_set_readonly(mr, false);
> 
> In case my error is not obvious, I meant:
> 
>    memory_region_init_ram_from_file(mr, ..., readonly=true, ...);
>    memory_region_set_readonly(mr, false);

Since the mmap was made using PROT_READ any store instructions to the
memory will fault.

Is there some scenario where memory_region_set_readonly() is called? I
can't find one.

Stefan

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