While trying to make KVM PR usable again, commit 5dfaa532ae introduced a
regression: the current compat_pvr value is passed to KVM instead of the
new one. This means that we always pass 0 instead of the max-cpu-compat
PVR during the initial machine reset. And at CAS time, we either pass
the PVR from the command line or even don't call kvmppc_set_compat() at
all, ie, the PCR will not be set as expected.
For example if we start a big endian fedora26 guest in power7 compat
mode on a POWER8 host, we get this in the guest:
$ cat /proc/cpuinfo
processor : 0
cpu : POWER7 (architected), altivec supported
clock : 4024.000000MHz
revision : 2.0 (pvr 004d 0200)
timebase : 512000000
platform : pSeries
model : IBM pSeries (emulated by qemu)
machine : CHRP IBM pSeries (emulated by qemu)
MMU : Hash
but the guest can still execute POWER8 instructions, and the following
program succeeds:
int main()
{
asm("vncipher 0,0,0"); // ISA 2.07 instruction
}
Let's pass the new compat_pvr to kvmppc_set_compat() and the program fails
with SIGILL as expected.
Reported-by: Nageswara R Sastry <rnsastry@linux.vnet.ibm.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
e4f0c6bb1a