Re: [PATCH v4 02/16] accel/tcg: Fix check for page writeability in load_atomic16_or_exit

[Richard Henderson]

On 5/30/23 07:48, Peter Maydell wrote:
> On Tue, 30 May 2023 at 15:29, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> > On 5/30/23 07:06, Peter Maydell wrote:
> > > > This is about falling through to the cmpxchg below: if !PAGE_WRITE_ORG, then 
> > > > the page is
> > > > really not writable, we will SIGSEGV, and handle_sigsegv_accerr_write will kill 
> > > > the process.
> > >
> > > Right, but if !PAGE_WRITE_ORG then that implies also !PAGE_WRITE,
> > > so we do that even without this change ?
> >
> > But !PAGE_WRITE does not imply !PAGE_WRITE_ORG.
>
> Hmm. In what situation do we mark a page writeable when the
> guest didn't ask for it to be writeable ?

I don't know -- it seems backward, I know.

I *think* it's a race condition, where PAGE_WRITE changes.
That's what the test case is trying to provoke, anyway.


r~