Hi Michael, Thanks for looking into the patch and your comments. On 2024/02/06 09:09 PM, Michael Ellerman wrote: > Hi Amit, > > One comment below ... > > Amit Machhiwal <amachhiw@xxxxxxxxxxxxx> writes: > > Currently, rebooting a pseries nested qemu-kvm guest (L2) results in > > below error as L1 qemu sends PVR value 'arch_compat' == 0 via > > ppc_set_compat ioctl. This triggers a condition failure in > > kvmppc_set_arch_compat() resulting in an EINVAL. > ... > > > > diff --git a/arch/powerpc/kvm/book3s_hv_nestedv2.c b/arch/powerpc/kvm/book3s_hv_nestedv2.c > > index 5378eb40b162..6042bdc70230 100644 > > --- a/arch/powerpc/kvm/book3s_hv_nestedv2.c > > +++ b/arch/powerpc/kvm/book3s_hv_nestedv2.c > > @@ -347,8 +348,26 @@ static int gs_msg_ops_vcpu_fill_info(struct kvmppc_gs_buff *gsb, > > break; > > } > > case KVMPPC_GSID_LOGICAL_PVR: > > - rc = kvmppc_gse_put_u32(gsb, iden, > > - vcpu->arch.vcore->arch_compat); > > + /* > > + * Though 'arch_compat == 0' would mean the default > > + * compatibility, arch_compat, being a Guest Wide > > + * Element, cannot be filled with a value of 0 in GSB > > + * as this would result into a kernel trap. > > + * Hence, when `arch_compat == 0`, arch_compat should > > + * default to L1's PVR. > > + * > > + * Rework this when PowerVM supports a value of 0 > > + * for arch_compat for KVM API v2. > > + */ > > Is there an actual plan that PowerVM will support this in future? > > If so, how will a future kernel know that it's running on a version of > PowerVM that does support arch_compat == 0? > > Similarly how will we know when it's OK to drop support for this > workaround? I'm sending a v4 based on an off mailing list discussion. > > cheers ~Amit
