Hi,
while looking through the code I found commit
f79116867ec80ed5d1d10043a3fd9ac8afd182c1 (upstream QEMU: enable SMEP)
which unconditionally propagates the bits from CPUID leaf 0x7 to the
guest. Though there is the KVM module in the line, this currently
whitelists three feature bits.
Doesn't that break migration? The result of the CPUID instruction the
guess issues only depends on the host and the KVM module's policy, not
on the CPU model QEMU uses. So I guess migrating from a newer CPU to an
older one breaks despite a rather conservative CPU model has been chosen
intentionally by the user.
The same is probably true for the VIA CPUID leaf.
Is that considered OK now or is that a bug? Shall the new feature bits
be made known to QEMU like the other ones on only enabled explicitly
(+smep) or by -cpu host?
I can make a patch for that if that is the right way to address this.
Regards,
Andre.
--
Andre Przywara
AMD-OSRC (Dresden)
Tel: x29712
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