On Tue, 30 May 2023 at 16:09, Richard Henderson <richard.hender...@linaro.org> wrote: > > On 5/30/23 07:48, Peter Maydell wrote: > > On Tue, 30 May 2023 at 15:29, Richard Henderson > > <richard.hender...@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.
That sounds like the theory I had earlier, that we don't have the mmap lock, so the other thread can get in and turn the RO-only-because-of-the-JIT page back to RW, so we don't want to do the non-atomic access for the "RO-only-because-of-JIT" cases. Reviewed-by: Peter Maydell <peter.mayd...@linaro.org> thanks -- PMM
