Ping
04.04.2019, 13:01, "Yury Kotov" <yury-ko...@yandex-team.ru>:
> I saw Catherine Ho's patch series and it seems ok to me, but in this RFC I
> asked
> about a way how to detect other writes which may not be covered by particular
> fixes.
> Perhaps this is excessive caution...
>
> Regards,
> Yury
>
> 04.04.2019, 12:52, "Dr. David Alan Gilbert" <dgilb...@redhat.com>:
>> * Юрий Котов (yury-ko...@yandex-team.ru) wrote:
>>> Ping
>>
>> Is this fixed by Catherine Ho's patch series?
>>
>> Dave
>>
>>> 21.03.2019, 19:27, "Yury Kotov" <yury-ko...@yandex-team.ru>:
>>> > Hi,
>>> >
>>> > 19.03.2019, 14:52, "Dr. David Alan Gilbert" <dgilb...@redhat.com>:
>>> >> * Peter Maydell (peter.mayd...@linaro.org) wrote:
>>> >>> On Tue, 19 Mar 2019 at 11:03, Dr. David Alan Gilbert
>>> >>> <dgilb...@redhat.com> wrote:
>>> >>> >
>>> >>> > * Peter Maydell (peter.mayd...@linaro.org) wrote:
>>> >>> > > I didn't think migration distinguished between "main memory"
>>> >>> > > and any other kind of RAMBlock-backed memory ?
>>> >>> >
>>> >>> > In Yury's case there's a distinction between RAMBlock's that are
>>> mapped
>>> >>> > with RAM_SHARED (which normally ends up as MAP_SHARED) and all
>>> others.
>>> >>> > You can set that for main memory by using -numa to specify a
>>> memdev
>>> >>> > that's backed by a file and has the share=on property.
>>> >>> >
>>> >>> > On x86 the ROMs end up as separate RAMBlock's that aren't affected
>>> >>> > by that -numa/share=on - so they don't fight Yury's trick.
>>> >>>
>>> >>> You can use the generic loader on x86 to load an ELF file
>>> >>> into RAM if you want, which would I think also trigger this.
>>> >>
>>> >> OK, although that doesn't worry me too much - since in the majority
>>> >> of cases Yury's trick still works well.
>>> >>
>>> >> I wonder if there's a way to make Yury's code to detect these cases
>>> >> and not allow the feature; the best thing for the moment would seem to
>>> >> be to skip the aarch test that uses elf loading.
>>> >
>>> > Currently, I've no idea how to detect such cases, but there is an
>>> ability to
>>> > detect memory corruption. I want to update the RFC patch to let user to
>>> map some
>>> > memory regions as readonly until incoming migration start.
>>> >
>>> > E.g.
>>> > 1) If x-ignore-shared is enabled in command line or memory region is
>>> marked
>>> > (something like ',readonly=on'),
>>> > 2) Memory region is shared (,share=on),
>>> > 3) And qemu is started with '-incoming' option
>>> >
>>> > Then map such regions as readonly until incoming migration finished.
>>> > Thus, the patch will be able to detect memory corruption and will not
>>> affect
>>> > normal cases.
>>> >
>>> > How do you think, is it needed?
>>> >
>>> > I already have a cleaner version of the RFC patch, but I'm not sure
>>> about 1).
>>> > Which way is better: enable capability in command line, add a new
>>> option for
>>> > memory-backend or something else.
>>> >
>>> >> Dave
>>> >>
>>> >>> thanks
>>> >>> -- PMM
>>> >> --
>>> >> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
>>> >
>>> > Regards,
>>> > Yury
>> --
>> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
