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

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

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@xxxxxxxxx>
> > >
> > >     
> > 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


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