Starting with Linux kernel v5.12 we dropped support[1] in KVM for
hosts that can't have their threads running in different MMU modes
(POWER9 < DD2.2). In these hosts, KVM will no longer report the
KVM_CAP_PPC_MMU_HASH_V3 capability[2] when the host is running Radix.
For guests that support both MMU modes, the negotiation during CAS
will make sure it selects the correct one.
For guests that only support Hash, such as P8 compat mode guests, the
following error is currently thrown:
$ ~/qemu-system-ppc64 -machine pseries,accel=kvm,max-cpu-compat=power8 ...
error: kvm run failed Invalid argument
NIP 0000000000000100 LR 0000000000000000 CTR 0000000000000000 XER 0000000000000000 CPU#0
MSR 8000000000001000 HID0 0000000000000000 HF 8000000000000000 iidx 3 didx 3
TB 00000000 00000000 DECR 0
GPR00 0000000000000000 0000000000000000 0000000000000000 000000007ff00000
GPR04 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR08 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR12 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR16 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR28 0000000000000000 0000000000000000 0000000000000000 0000000000000000
CR 00000000 [ - - - - - - - - ] RES ffffffffffffffff
SRR0 0000000000000000 SRR1 0000000000000000 PVR 00000000004e1201 VRSAVE 0000000000000000
SPRG0 0000000000000000 SPRG1 0000000000000000 SPRG2 0000000000000000 SPRG3 0000000000000000
SPRG4 0000000000000000 SPRG5 0000000000000000 SPRG6 0000000000000000 SPRG7 0000000000000000
HSRR0 0000000000000000 HSRR1 0000000000000000
CFAR 0000000000000000
LPCR 000000000004f01f
PTCR 0000000000000000 DAR 0000000000000000 DSISR 0000000000000000
This patch adds a verification during the writing of the platform
support vector so that we error out as soon as we determine this guest
only supports Hash and the host doesn't.
~/qemu-system-ppc64 -machine pseries,accel=kvm,max-cpu-compat=power8 ...
qemu-system-ppc64: Guest requested unavailable MMU mode (hash).
1- https://git.kernel.org/torvalds/p/b1b1697ae0cc8
2- https://git.kernel.org/torvalds/p/a722076e94702
Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Message-Id: <20210505001130.3999968-3-farosas@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
ab5add4c7b