Thanks for Ian's answer. it comes to a more general scenario.
Hi Chu, EPT entry is 64 bit long, regardless the hypervisor is on
x86_32 platform or x86_64 platform. So there is no difference for
the hypervisor to use EPT on these two platforms.
On 11/17/2010 7:26 PM, Chu Rui wrote:
Okay, in my mind, the hardware has only one work mode, 32bit
or 64bit. Thus the 32bit guest address will be extended under
the 64bit host.
But what will happen for a 64bit guest under a 32bit host :-)
2010/11/17 Ian Campbell <Ian.Campbell@xxxxxxxxxx>
On Wed, 2010-11-17 at 10:32 +0000, George
Dunlap wrote:
> The exact implementation of 32-bit mode on a 64-bit
capable processor
> is something only the engineers at Intel know; but
logically yes,
> whatever it does is equivalent to first zero-extending
the 32-bit
> value.
Even on x86_32 physical addresses are >32 bit (think PAE).
cr3 is a
physical address, even if the register which exposes it
happens to be
limited to 32 bits. cr3 has probably already been expanded to
a full
physical address by the time EPT sees it and I don't think
there's any
difference between 32 and 64 bit (at least in this aspect) in
how EPT
handles the translation from physical address to machine
address.
Ian.
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