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Fri, 07 Aug 2026 05:15:03 -0700 (PDT) Received: from pve-server ([49.205.216.49]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-315be86d3fcsm7231096eec.4.2026.08.07.05.14.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Aug 2026 05:15:02 -0700 (PDT) From: Ritesh Harjani (IBM) To: Amit Machhiwal Cc: Amit Machhiwal , linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan , Vaibhav Jain , 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, Gautam Menghani Subject: Re: [PATCH v7 3/4] KVM: PPC: Book3S HV: Add support for compat CPU capabilities for KVM on PowerNV In-Reply-To: <20260807170704.3280f54c-e2-amachhiw@linux.ibm.com> Date: Fri, 07 Aug 2026 17:43:07 +0530 Message-ID: <7bm2ku24.ritesh.list@gmail.com> References: <20260806170645.11892-1-amachhiw@linux.ibm.com> <20260806170645.11892-4-amachhiw@linux.ibm.com> <20260807170704.3280f54c-e2-amachhiw@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Amit Machhiwal writes: > On 2026/08/07 10:24 AM, Ritesh Harjani wrote: >> Amit Machhiwal writes: > > > >> > >> > static int kvmppc_get_compat_caps(struct kvm_ppc_compat_caps *host_caps) >> > { >> > + struct device_node *np; >> > unsigned long capabilities = 0; >> > long rc = -EINVAL; >> > + u32 cpu_version = 0; >> > >> > if (kvmhv_on_pseries()) { >> > if (kvmhv_is_nestedv2()) { >> > WARN_ON_ONCE(!nested_capabilities); >> > capabilities = nested_capabilities; >> > rc = 0; >> > + } else { >> > + for_each_node_by_type(np, "cpu") { >> > + if (!of_property_read_u32(np, "cpu-version", >> > + &cpu_version)) { >> > + of_node_put(np); >> > + break; >> > + } >> > + } >> >> What happens when we don't have "cpu-version" DT property? >> Check this commit >> 5a61ef74f269f2 ("powerpc/64s: Support new device tree binding for discovering CPU features") >> >> And also why do we need to parse the DT properties again? >> Shouldn't we check something like this? >> >> if (cpu_has_feature(CPU_FTR_P11_PVR)) >> capabilities |= KVM_PPC_COMPAT_CAP_POWER11; >> if (cpu_has_feature(CPU_FTR_ARCH_31)) >> capabilities |= KVM_PPC_COMPAT_CAP_POWER10; >> if (cpu_has_feature(CPU_FTR_ARCH_300)) >> capabilities |= KVM_PPC_COMPAT_CAP_POWER9; >> > > Thanks for the suggestion, Ritesh! After closer analysis, cpu_has_feature() > would give the same result on pseries, but I believe that using 'cpu-version' > directly is both more correct and more explicit for this context. > > Here's why: > > 1. 'ibm,powerpc-cpu-features' / dt-cpu-ftrs is baremetal (powernv/OPAL) only. Arghh. That make sense. Thanks for checking. The design with "cpu-version" sounds good in that case. Please feel free to add: Reviewed-by: Ritesh Harjani (IBM)