Re: [Qemu-devel] [PULL 12/13] page_unprotect(): handle calls to pages that are PAGE_WRITE

[Laurent Vivier]

Le 22/03/2018 à 12:13, Laurent Vivier a écrit :
> Le 22/03/2018 à 12:07, Peter Maydell a écrit :
>> On 22 March 2018 at 11:05, Peter Maydell <address@hidden> wrote:
>>> On 22 March 2018 at 10:36, Laurent Vivier <address@hidden> wrote:
>>>> It goes wrong in this part:
>>>>
>>>> +     */
>>>> +    if (is_write && info->si_signo == SIGSEGV && info->si_code ==
>>>> SEGV_ACCERR &&
>>>> +        h2g_valid(address)) {
>>>>
>>>> Because, on ppc, si_code is SEGV_MAPERR and not SEGV_ACCERR
>>>> (on x86_64, si_code is SEGV_ACCERR as expected)
>>>
>>> So on PPC if you have a page mapped, and you access it with
>>> the wrong permissions, you get SEGV_MAPERR? This seems like
>>> a host kernel bug to me.
>>
>> ...in particular, kernel commit ecb101aed86156e (dated Dec 2017)
>> fixes a regression introduced in commit c3350602e876 that broke
>> the ppc kernels so they started returning SEGV_MAPERR here
>> instead of SEGV_ACCERR. Presumably your host kernel is missing
>> this fix.
> 
> Yes, you're right, my kernel is 4.14-rc1 (6e80ecd) with
> c3350602e876 but without ecb101aed86156e.
> 
> I'm going to update it.

Re-tested with 4.16-rc6 on ppc32 and it works fine.

Thanks,
Laurent