On Thu, 14 Sep 2017 13:17:48 +0200 Thomas Huth <th...@redhat.com> wrote:
> On 14.09.2017 12:48, Greg Kurz wrote:
> > If the host has both KVM PR and KVM HV loaded and we pass:
> >
> > -machine pseries,accel=kvm,kvm-type=PR
> >
> > the kvmppc_is_pr() returns false instead of true. Since the helper
> > is mostly used as fallback, it doesn't have any real impact with
> > recent kernels. A notable exception is the workaround to allow
> > migration between compatible hosts with different PVRs (eg, POWER8
> > and POWER8E), since KVM still doesn't provide a way to check if a
> > specific PVR is supported (see commit c363a37a450f for details).
> >
> > According to the official KVM API documentation [1], KVM_PPC_GET_PVINFO
> > is "vm ioctl", but we check it as a global ioctl. The following function
> > in KVM is hence called with kvm == NULL and considers we're in HV mode.
> >
> > int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> > {
> > int r;
> > /* Assume we're using HV mode when the HV module is loaded */
> > int hv_enabled = kvmppc_hv_ops ? 1 : 0;
> >
> > if (kvm) {
> > /*
> > * Hooray - we know which VM type we're running on. Depend on
> > * that rather than the guess above.
> > */
> > hv_enabled = is_kvmppc_hv_enabled(kvm);
> > }
> >
> > Let's use kvm_vm_check_extension() to fix the issue.
>
> By the way, what about the other CAPs that rely on hv_enabled? grepping
> through the QEMU sources, I can see:
>
> cap_ppc_smt = kvm_check_extension(s, KVM_CAP_PPC_SMT);
>
> cap_htab_fd = kvm_check_extension(s, KVM_CAP_PPC_HTAB_FD);
>
> int ret = kvm_check_extension(s, KVM_CAP_NR_VCPUS);
>
> return kvm_check_extension(kvm_state, KVM_CAP_SYNC_MMU);
>
> !kvm_check_extension(cs->kvm_state, KVM_CAP_SW_TLB)) {
>
> ... do we need to fix them, too?
>
I'm currently going through the KVM code to see which ones need to be
fixed. I'll send more patches shortly :)
Cheers,
--
Greg
> Thomas
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