Re: [Qemu-devel] virsh dump (qemu guest memory dump?): KASLR enabled linux guest support

[Dave Young]

On 11/09/16 at 11:58am, Wen Congyang wrote:
> On 11/09/2016 11:17 AM, Dave Young wrote:
> > Drop qiaonuohan, seems the mail address is wrong..
> > 
> > On 11/09/16 at 11:01am, Dave Young wrote:
> >> Hi,
> >>
> >> Latest linux kernel enabled kaslr to randomiz phys/virt memory
> >> addresses, we had some effort to support kexec/kdump so that crash
> >> utility can still works in case crashed kernel has kaslr enabled.
> >>
> >> But according to Dave Anderson virsh dump does not work, quoted messages
> >> from Dave below:
> >>
> >> """
> >> with virsh dump, there's no way of even knowing that KASLR
> >> has randomized the kernel __START_KERNEL_map region, because there is no
> >> virtual address information -- e.g., like "SYMBOL(_stext)" in the kdump
> >> vmcoreinfo data to compare against the vmlinux file symbol value.
> >> Unless virsh dump can export some basic virtual memory data, which
> >> they say it can't, I don't see how KASLR can ever be supported.
> >> """
> >>
> >> I assume virsh dump is using qemu guest memory dump facility so it
> >> should be first addressed in qemu. Thus post this query to qemu devel
> >> list. If this is not correct please let me know.
> 
> IIRC, 'virsh dump --memory-only' uses dump-guest-memory, and 'virsh dump'
> uses migration to dump.

Do they need different fixes? Dave, I guess you mean --memory-only, but
could you clarify and confirm it?

> 
> I think I should study kaslr first...

Thanks for taking care of it.

> 
> Thanks
> Wen Congyang
> 
> >>
> >> Could you qemu dump people make it work? Or we can not support virt dump
> >> as long as KASLR being enabled. Latest Fedora kernel has enabled it in 
> >> x86_64.
> >>
> >> Thanks
> >> Dave
> > 
> > 
> > 
> 
> 
>