Re: [PATCH 2/2] x86/cpu: Handle GUEST_MAXPHYADDR < HOST_MAXPHYADDR for hosts that don't support it
On Fri, Jul 10, 2020 at 09:22:42AM +0200, Paolo Bonzini wrote:
On 09/07/20 21:13, Eduardo Habkost wrote:
>> Doesn't this require intercepting MOV-to-CR3 when the guest is in PAE
>> mode, so that the hypervisor can validate the high bits in the PDPTEs?
> If the fix has additional overhead, is the additional overhead
> bad enough to warrant making it optional? Most existing
> GUEST_MAXPHYADDR < HOST_MAXPHYADDR guests already work today
> without the fix.
The problematic case is when host maxphyaddr is 52. That case wouldn't
work at all without the fix.
What can QEMU do to do differentiate "can't work at all without
the fix" from "not the best idea, but will probably work"?
--
Eduardo