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Wed, 10 Jun 2026 15:53:15 +0000 (GMT) Received: from fedora (unknown [9.5.7.39]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 10 Jun 2026 15:53:15 +0000 (GMT) Date: Wed, 10 Jun 2026 21:23:17 +0530 From: Amit Machhiwal To: Vaibhav Jain Cc: Amit Machhiwal , linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan , Anushree Mathur , Paolo Bonzini , Nicholas Piggin , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Jonathan Corbet , Shuah Khan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, lkp@intel.com Subject: Re: [PATCH v3 4/5] KVM: PPC: Book3S HV: Add support for compat CPU capabilities for KVM on PowerNV Message-ID: <20260610212254.3cec19b0-ef-amachhiw@linux.ibm.com> Mail-Followup-To: Vaibhav Jain , linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan , Anushree Mathur , Paolo Bonzini , Nicholas Piggin , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Jonathan Corbet , Shuah Khan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, lkp@intel.com References: <20260522152744.55251-1-amachhiw@linux.ibm.com> <20260522152744.55251-5-amachhiw@linux.ibm.com> <87jysgz292.fsf@vajain21.in.ibm.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87jysgz292.fsf@vajain21.in.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=b4uCJNGx c=1 sm=1 tr=0 ts=6a298873 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=kj9zAlcOel0A:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=C8Vz2Ujs2r1iiY_tozkA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: QS9JKwRuI7EoydCswWm4uUnL-s98AkHl X-Proofpoint-GUID: 3aN2sU-fgy2MYeKTz0nVVxtBonT1tyqA X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjEwMDE0OCBTYWx0ZWRfX1EnIf+YbxpRy 5srb6zES9vsIinzvkbAQkr395H2uGvsOyOp8qiVIgTFdPlCiMkyHXSyJ+Eqgtb0XhTyD8j5PtzR v98Zcfe72P8lCipU5X0KKLmMWKNmW2wUoUXmDVOJe8eIyha+SglKBFqSW+WSQEV/sEhl9o9kIxY ezjZUxxJ5bqT+zOd8W+J0YvcWhjygs5yN5lcPfCFbtEdtBjWE1d1re/XzzsvPmvAQd8ZyofOsNm 9uTlFEWoal7hLg36rY9pJkjIFIQ6+MKrT7xxw2wn3Q79v9+9TUa07640Rt/6J/ERJhjoiiPyUmD vuwCIZ/aCOWo3jZV3zNhrf6eli+Au9Bovsm7MFIlTNSd9/JkDpOi5xlTgUkOmWx90kygmxwyy6K SLnwb9VKDgy0bPTGMRKYrvG+ZUEvEqbuxcUQZjDs8xMG22BN0ho20SHOnNYpByh6z1jPDSy64k+ tZxQSK7Sig5c87Dp0jg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-10_03,2026-06-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 bulkscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 malwarescore=0 impostorscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606100148 On 2026/06/03 09:47 AM, Vaibhav Jain wrote: > Hi Amit, > > Thanks for the patch. My review comments inline: > > Amit Machhiwal 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. > > > > Introduce a helper to translate CPU version values into compatibility > > capability bits and integrate it into kvmppc_get_compat_cpu_caps(). > > > > 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 > > Tested-by: Anushree Mathur > > Signed-off-by: Amit Machhiwal > > --- > > 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 38de7040e2b7..18774c49af85 100644 > > --- a/arch/powerpc/kvm/book3s_hv.c > > +++ b/arch/powerpc/kvm/book3s_hv.c > > @@ -6522,15 +6522,50 @@ 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 |= H_GUEST_CAP_POWER11; > > + break; > > + case PVR_ARCH_31: > > + *capabilities |= H_GUEST_CAP_POWER10; > > + break; > > + case PVR_ARCH_300: > > + *capabilities |= H_GUEST_CAP_POWER9; > > + break; > > + default: > > + return -EINVAL; > > + } > > + > > + return 0; > > +} > > > > static int kvmppc_get_compat_cpu_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); > Need to mask capabilities as mentioned in the review comments for > previous patch. I would suggest creating a helper that performs the > hcall and applies the mask which can then be used at > plpar_guest_get_capabilities() call sites. Sure, will do. Thanks, Amit > > > + } 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); > > + } > > host_caps->compat_capabilities = capabilities; > > } > > > > -- > > 2.50.1 (Apple Git-155) > > > > -- > Cheers > ~ Vaibhav