Re: [Xen-devel] [Patch] Qemu map cache

[Anthony Liguori <aliguori@xxxxxxxxxxxxxxxxxx>]

Cui, Dexuan wrote:
> On IA32 host or IA32 PAE host, at present, generally, we can't create an
> HVM guest with more than 2G memory, because generally it's almost
> impossible for Qemu to find a large enough and consecutive virtual
> address space to map an HVM guest's whole physical address space.
> The attached patch fixes this issue using dynamic mapping based on
> little blocks of memory.
>   
(Sorry if this comes through twice).

Have you considered doing something similar for mainline QEMU?  The 
reason I ask is that V2E pulls in all of the dynamic translation code.  
My initial reaction is that doing map cache will require a significant 
amount change to the dynamic translation bits since we can no longer 
make the assumption that memory can be accessed directly.  I don't fully 
have my head around it yet, but this may involve lots of nastiness with 
keeping track of which TB's reference what memory and invalidating those 
TBs when map cache references are invalidated.  The QEMU TLB may 
simplify some of this but I'm not entirely sure.
Have you given this any thought?

Thanks,

Anthony Liguori

> -- Dexuan Cui
>
> Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>
>
>   
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