[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [RFC PATCH] QEMU may write to system_memory before gues
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC PATCH] QEMU may write to system_memory before guest starts |
Date: |
Thu, 4 Apr 2019 10:52:12 +0100 |
User-agent: |
Mutt/1.11.3 (2019-02-01) |
* Юрий Котов (address@hidden) wrote:
> Ping
Is this fixed by Catherine Ho's patch series?
Dave
> 21.03.2019, 19:27, "Yury Kotov" <address@hidden>:
> > Hi,
> >
> > 19.03.2019, 14:52, "Dr. David Alan Gilbert" <address@hidden>:
> >> * Peter Maydell (address@hidden) wrote:
> >>> On Tue, 19 Mar 2019 at 11:03, Dr. David Alan Gilbert
> >>> <address@hidden> wrote:
> >>> >
> >>> > * Peter Maydell (address@hidden) 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 / address@hidden / Manchester, UK
> >
> > Regards,
> > Yury
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK