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

[Wen Congyang <wency@cn.fujitsu.com>]

On 11/09/2016 01:02 PM, Dave Young wrote:
> 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.

Can you give me the patch for kexec/kdump. I want to know what I need to do
for dump-guest-memory.

Thanks
Wen Congyang

> 
>>
>> 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
>>>
>>>
>>>
>>
>>
>>
> 
> 
> .
>