Hi Amit. Thanks for the patch and incorporating V3 review comments. Further review comments inline below:
Amit Machhiwal <[email protected]> writes: > Currently, when booting a compatibility-mode KVM guest (L1) on a PowerNV > hypervisor (L0), the guest runs with the expected processor > compatibility level. However, when booting a nested KVM guest (L2) > inside the L1, QEMU derives the CPU model from the raw host PVR and > attempts to run the nested guest at that level, instead of honoring the > compatibility mode of the L1. > > Extend host CPU compatibility capability reporting to support nested > virtualization on PowerNV systems (PAPR nested API v1). > > For nested API v2 (PowerVM), compatibility capabilities are obtained > from the hypervisor via the H_GUEST_GET_CAPABILITIES hcall. This > information is not available on PowerNV systems. > > For nested API v1, derive the compatibility capabilities from the L1 > guest by reading the "cpu-version" property from the device tree, which > reflects the effective (logical) processor compatibility level. Map this > value to the corresponding compatibility capability bitmap using > KVM-specific constants. > > Introduce a helper to translate CPU version values into KVM_PPC_COMPAT_CAP > bits and integrate it into kvmppc_get_compat_caps(). The implementation > applies masking to ensure only supported processor modes are exposed. > > This allows userspace to query host CPU compatibility modes on both > PowerVM and PowerNV platforms via the KVM_PPC_GET_COMPAT_CAPS ioctl. > > Suggested-by: Vaibhav Jain <[email protected]> > Signed-off-by: Amit Machhiwal <[email protected]> > --- > arch/powerpc/kvm/book3s_hv.c | 37 +++++++++++++++++++++++++++++++++++- > 1 file changed, 36 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index f674386df62c..375e7a7fa9f8 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -6523,15 +6523,50 @@ static bool kvmppc_hash_v3_possible(void) > return true; > } > > +static int kvmppc_map_compat_capabilities(const __be32 cpu_version, > + unsigned long *capabilities) > +{ > + switch (cpu_version) { > + case PVR_ARCH_31_P11: > + *capabilities |= KVM_PPC_COMPAT_CAP_POWER11; Do you need to do 'break' here instead of falling through. Since P11 host can support P10 and P9 compat modes > + break; > + case PVR_ARCH_31: > + *capabilities |= KVM_PPC_COMPAT_CAP_POWER10; > + break; > + case PVR_ARCH_300: > + *capabilities |= KVM_PPC_COMPAT_CAP_POWER9; > + break; > + default: > + return -EINVAL; > + } > + > + return 0; > +} > > static int kvmppc_get_compat_caps(struct kvm_ppc_compat_caps *host_caps) > { > + struct device_node *np; > unsigned long capabilities = 0; > + const __be32 *prop = NULL; > long rc = -EINVAL; > + u32 cpu_version; > > if (kvmhv_on_pseries()) { > - if (kvmhv_is_nestedv2()) > + if (kvmhv_is_nestedv2()) { > rc = plpar_guest_get_capabilities(0, &capabilities); > + } else { > + for_each_node_by_type(np, "cpu") { > + prop = of_get_property(np, "cpu-version", NULL); > + if (prop) { > + cpu_version = be32_to_cpup(prop); > + break; > + } > + } > + if (!prop) > + return -EINVAL; > + rc = kvmppc_map_compat_capabilities(cpu_version, > + &capabilities); > + } should you check for 'rc' error here before assigning 'capabilities' to 'host_caps->compat_capabilities' . I understand it will be set to '0' due to its initialization at the top of the function. But would be better to make it more explicit > host_caps->compat_capabilities = capabilities & > KVM_PPC_COMPAT_BITMASK; > } > -- > 2.50.1 (Apple Git-155) > > -- Cheers ~ Vaibhav
