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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 12 Aug 2009, Zhai, Edwin wrote:
> 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...
> 

For vga screen refresh qemu calls xc_hvm_track_dirty_vram and
then cpu_physical_memory_set_dirty; the latter needs only to call
xc_hvm_modified_memory in case logdirty is active.
In facts your patch is modifying logdirty_bitmap only when
logdirty_bitmap != NULL that is when a logdirty event is triggered on
xenstore.


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