[Qemu-ppc] [PATCH] target/ppc: Only set PCR in kvm if actually in a compat mode

[Suraj Jitindar Singh]

The Processor Compatibility Register (PCR) I used to set the
compatibility mode of the processor using the SET_ONE_REG ioctl on
KVM_REG_PPC_ARCH_COMPAT. Previously this was only called when a compat
mode was actually in use, however a recent patch made it unconditional.
Calling this in KVM_PR fails as there is no handler for that call and it
is thus impossible to start a machine with KVM_PR.

Change ppc_set_compat() so that the ioctl is only actually called if a
compat mode is in use. This means that a KVM_PR guest can boot.
Additionally the current behaviour for KVM_HV is preserved where a compat
mode of 0 set pcr and arch_compat in the vcore struct to zero, both of
which are initialised to zero anyway.

Fixes: 37f516defa2e ("pseries: Reset CPU compatibility mode")

Signed-off-by: Suraj Jitindar Singh <address@hidden>

---

Based on: dwg/ppc-for-2.10

 target/ppc/compat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/ppc/compat.c b/target/ppc/compat.c
index f1b67fa..4482206 100644
--- a/target/ppc/compat.c
+++ b/target/ppc/compat.c
@@ -143,7 +143,7 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr, 
Error **errp)
     cpu->compat_pvr = compat_pvr;
     env->spr[SPR_PCR] = pcr & pcc->pcr_mask;
 
-    if (kvm_enabled()) {
+    if (kvm_enabled() && compat_pvr) {
         int ret = kvmppc_set_compat(cpu, cpu->compat_pvr);
         if (ret < 0) {
             error_setg_errno(errp, -ret,
-- 
2.9.4