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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
