On Tue, 15 Aug 2017 14:04:09 +1000 David Gibson <da...@gibson.dropbear.id.au> wrote:
> On Mon, Aug 14, 2017 at 07:49:16PM +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. > > I'm not sure that's true any more, since we now prefer compat modes > during CAS. I guess we could exclude the compat modes from the Oops, I wanted to talk about CAS and I... forgot :( So, indeed, CAS fails to apply compat mode and immediately returns H_HARDWARE to the guest, ie the rest of CAS isn't done :-\. Linux guests print a warning: WARNING: ibm,client-architecture-support call FAILED! done and (luckily?) continue to boot anyway (at least that's what happens with RHEL7 guests). > advertised list based on what KVM supports, but that seems pretty > awkward. > I'll re-read the details in LoPAPR and try to come up with something. Cheers, -- Greg > > 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> > > In any case, this makes things better than they were, so I'm applying. > > > --- > > 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 { > > >
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