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Tue, 08 Jul 2025 15:34:37 -0700 (PDT) Date: Tue, 08 Jul 2025 22:34:35 +0000 In-Reply-To: (message from Mark Rutland on Mon, 7 Jul 2025 17:05:00 +0100) Mime-Version: 1.0 Message-ID: Subject: Re: [PATCH v3 01/22] arm64: cpufeature: Add cpucap for HPMN0 From: Colton Lewis To: Mark Rutland Cc: kvm@vger.kernel.org, pbonzini@redhat.com, corbet@lwn.net, linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, mizhang@google.com, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, shuah@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-perf-users@vger.kernel.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250708_153439_067701_BA8F0859 X-CRM114-Status: GOOD ( 18.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Mark Rutland writes: > On Thu, Jun 26, 2025 at 08:04:37PM +0000, Colton Lewis wrote: >> Add a capability for FEAT_HPMN0, whether MDCR_EL2.HPMN can specify 0 >> counters reserved for the guest. >> This required changing HPMN0 to an UnsignedEnum in tools/sysreg >> because otherwise not all the appropriate macros are generated to add >> it to arm64_cpu_capabilities_arm64_features. > I agree it's appropriate to mark ID_AA64DFR0_EL1.HPMN0 as an > UnsignedEnum. It follows the usual ID scheme per ARM DDI 0487 L.a > section D24.1.3, and zero means not present, so it must be unsigned. > Likewise, the value renames (UNPREDICTABLE => NI and DEF => IMP) look > fine to me. >> Signed-off-by: Colton Lewis > I have one minor nit below, but either way: > Acked-by: Mark Rutland Thank you Mark >> --- >> arch/arm64/kernel/cpufeature.c | 8 ++++++++ >> arch/arm64/tools/cpucaps | 1 + >> arch/arm64/tools/sysreg | 6 +++--- >> 3 files changed, 12 insertions(+), 3 deletions(-) >> diff --git a/arch/arm64/kernel/cpufeature.c >> b/arch/arm64/kernel/cpufeature.c >> index b34044e20128..73a7dac4b6f6 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -548,6 +548,7 @@ static const struct arm64_ftr_bits ftr_id_mmfr0[] = { >> }; >> static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = { >> + ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, >> ID_AA64DFR0_EL1_HPMN0_SHIFT, 4, 0), >> S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, >> ID_AA64DFR0_EL1_DoubleLock_SHIFT, 4, 0), >> ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, >> ID_AA64DFR0_EL1_PMSVer_SHIFT, 4, 0), >> ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, >> ID_AA64DFR0_EL1_CTX_CMPs_SHIFT, 4, 0), >> @@ -2896,6 +2897,13 @@ static const struct arm64_cpu_capabilities >> arm64_features[] = { >> .matches = has_cpuid_feature, >> ARM64_CPUID_FIELDS(ID_AA64MMFR0_EL1, FGT, FGT2) >> }, >> + { >> + .desc = "FEAT_HPMN0", > Minor nit, but we can drop the "FEAT_" prefix here, for consistency with > other features (e.g. E0PD, FPMR). > Mark. Will do. >> + .type = ARM64_CPUCAP_SYSTEM_FEATURE, >> + .capability = ARM64_HAS_HPMN0, >> + .matches = has_cpuid_feature, >> + ARM64_CPUID_FIELDS(ID_AA64DFR0_EL1, HPMN0, IMP) >> + }, >> #ifdef CONFIG_ARM64_SME >> { >> .desc = "Scalable Matrix Extension", >> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps >> index 10effd4cff6b..5b196ba21629 100644 >> --- a/arch/arm64/tools/cpucaps >> +++ b/arch/arm64/tools/cpucaps >> @@ -39,6 +39,7 @@ HAS_GIC_CPUIF_SYSREGS >> HAS_GIC_PRIO_MASKING >> HAS_GIC_PRIO_RELAXED_SYNC >> HAS_HCR_NV1 >> +HAS_HPMN0 >> HAS_HCX >> HAS_LDAPR >> HAS_LPA2 >> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg >> index 8a8cf6874298..d29742481754 100644 >> --- a/arch/arm64/tools/sysreg >> +++ b/arch/arm64/tools/sysreg >> @@ -1531,9 +1531,9 @@ EndEnum >> EndSysreg >> Sysreg ID_AA64DFR0_EL1 3 0 0 5 0 >> -Enum 63:60 HPMN0 >> - 0b0000 UNPREDICTABLE >> - 0b0001 DEF >> +UnsignedEnum 63:60 HPMN0 >> + 0b0000 NI >> + 0b0001 IMP >> EndEnum >> UnsignedEnum 59:56 ExtTrcBuff >> 0b0000 NI >> -- >> 2.50.0.727.gbf7dc18ff4-goog