Re: [PATCH] [IOEMU]: fix the crash of HVM live migration with intensive disk access

["Zhai, Edwin" <edwin.zhai@intel.com>]

Gianluca,

Do you have comments for this? Maybe Stefano and I are on the same page. 
My assumption is that we need keep the cpu_physical_memory_set_dirty and 
phys_ram_dirty for qemu itself, and make  cpu_physical_memory_set_dirty 
call xc_hvm_modified_memory if in live migration.

Thanks,


Zhai, Edwin wrote:
>
>
> Stefano Stabellini wrote:
>> On Tue, 11 Aug 2009, Zhai, Edwin wrote:
>>  
>>>  [IOEMU]: fix the crash of HVM live migration with intensive disk 
>>> access
>>>
>>> Intensive disk access, e.g. sum of big file, during HVM live 
>>> migration would cause guest error even file system crash. Guest 
>>> dmesg said
>>> "attempt to access beyond end of device
>>> hda1: rw=0, want=10232032112, limit=10474317"
>>>
>>> Current map cache used by qemu dma doesn't mark the page dirty, so 
>>> that these pages(probably holding DMA data struct) are not 
>>> transferred in the last iteration during live migration.
>>>
>>> This patch fixes it, and also merges the qemu's original dirty 
>>> bitmap used by other devices such as vga.
>>>
>>> Signed-Off-By: Zhai Edwin <edwin.zhai@intel.com>
>>>
>>>     
>>
>> I think the fix is correct but we should thinking about dropping
>> logdirty and start using xc_hvm_modified_memory instead for all cases.
>>   
>
> One interface should be better. But I'm not sure about the perf 
> implications. You know, qemu use logdirty for its device emulation 
> even without live migration, e.g. vga screen refresh. Changing to 
> xc_hvm_modified_memory would cause many hypercall to set/get the 
> bitmap in xen...
>
>> I think Gianluca also may have something to say about this but this week
>> he is on vacation.
>>
>>   
>

-- 
best rgds,
edwin