Re: [PATCH] softmmu/memory: Validate {read, write}_with_attrs before calling

[Peter Maydell]

On Sun, 5 Sept 2021 at 17:49, Bin Meng <bmeng.cn@gmail.com> wrote:
>
> On Mon, Sep 6, 2021 at 12:29 AM Peter Maydell <peter.maydell@linaro.org> 
> wrote:
> >
> > On Sun, 5 Sept 2021 at 16:40, Bin Meng <bmeng.cn@gmail.com> wrote:
> > >
> > > {read,write}_with_attrs might be missing, and the codes currently do
> > > not validate them before calling, which will cause segment fault.
> > >
> > > Fixes: 62a0db942dec ("memory: Remove old_mmio accessors")
> > > Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
> >
> > This 'fixes' tag doesn't seem quite right. Before that
> > commit 62a0db942dec, we still required that a MemoryRegionOps
> > provided some form of both read and write.
>
> Did you mean before commit 62a0db942dec leaving MemoryRegionOps NULL
> was not allowed, but things changed so that now it's possible to have
> NULL MemoryRegionOps? If yes, then the commit id of "Fixes" should
> probably go to the changes that allowed NULL memory ops. If not, I
> don't think "Fixes" tag is wrong.

I mean that before commit 62a0db942dec leaving the pointers all
NULL was not allowed, and after that commit leaving the pointers all
NULL was still not allowed. It's been a requirement that you
provide at least one function pointer for read and one for
write ever since the MemoryRegion APIs were introduced in 2012.
You're proposing an API change; it might be a good one, but it
isn't a 'Fixes' to anything.

-- PMM