On Mon, 2017-08-14 at 19:49 +0200, Greg Kurz wrote: > When running in KVM PR mode, kvmppc_set_compat() always fail because > the > current PR implementation doesn't handle KVM_REG_PPC_ARCH_COMPAT. Now > that > the machine code inconditionally calls ppc_set_compat_all() at reset > time > to restore the compat mode default value (commit 66d5c492dd3a9), it > is > impossible to start a guest with PR: > > qemu-system-ppc64: Unable to set CPU compatibility mode in KVM: > Invalid argument > > A tentative patch [1] was recently sent by Suraj to address the > issue, but > it would prevent the compat mode to be turned off on reset. And we > really > don't want to explicitely check for KVM PR. During the patch's > review, > David suggested that we should only call the KVM ioctl() if the > compat > PVR changes. This allows at least to run with KVM PR, provided no > compat > mode is requested from the command line (which should be the case > when > running PR nested). This is what this patch does. > > While here, we also fix the side effect where KVM would fail but we > would > change the CPU state in QEMU anyway. > > [1] http://patchwork.ozlabs.org/patch/782039/ > > Signed-off-by: Greg Kurz <gr...@kaod.org>
I meant to send a follow up but it fell on my priority list so thanks for this Looks good to me Reviewed-by: Suraj Jitindar Singh <sjitindarsi...@gmail.com> > --- > target/ppc/compat.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/target/ppc/compat.c b/target/ppc/compat.c > index f1b67faa97e3..f8729fe46d61 100644 > --- a/target/ppc/compat.c > +++ b/target/ppc/compat.c > @@ -140,16 +140,17 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t > compat_pvr, Error **errp) > > cpu_synchronize_state(CPU(cpu)); > > - cpu->compat_pvr = compat_pvr; > - env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > - > - if (kvm_enabled()) { > + if (kvm_enabled() && cpu->compat_pvr != compat_pvr) { > int ret = kvmppc_set_compat(cpu, cpu->compat_pvr); > if (ret < 0) { > error_setg_errno(errp, -ret, > "Unable to set CPU compatibility mode > in KVM"); > + return; > } > } > + > + cpu->compat_pvr = compat_pvr; > + env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > } > > typedef struct { >