linux-kernel - [RFC PATCH 1/7] arm64: cpufeature: Add API to report system support of HWDBM

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Message-ID: <20210126124444.27136-2-zhukeqian1@huawei.com>
Date:   Tue, 26 Jan 2021 20:44:38 +0800
From:   Keqian Zhu <zhukeqian1@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kvm@...r.kernel.org>,
        <kvmarm@...ts.cs.columbia.edu>, Marc Zyngier <maz@...nel.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>
CC:     Alex Williamson <alex.williamson@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Robin Murphy <robin.murphy@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        <wanghaibin.wang@...wei.com>, <jiangkunkun@...wei.com>,
        <xiexiangyou@...wei.com>, <zhengchuan@...wei.com>,
        <yubihong@...wei.com>
Subject: [RFC PATCH 1/7] arm64: cpufeature: Add API to report system support of HWDBM

Though we already has a cpu capability named ARM64_HW_DBM, it's a
LOCAL_CPU cap and conditionally compiled by CONFIG_ARM64_HW_AFDBM.

This reports the system wide support of HW_DBM.

Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
---
 arch/arm64/include/asm/cpufeature.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 9a555809b89c..dfded86c7684 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -664,6 +664,18 @@ static inline bool system_supports_mixed_endian(void)
 	return val == 0x1;
 }
 
+static inline bool system_supports_hw_dbm(void)
+{
+	u64 mmfr1;
+	u32 val;
+
+	mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
+	val = cpuid_feature_extract_unsigned_field(mmfr1,
+						ID_AA64MMFR1_HADBS_SHIFT);
+
+	return val == 0x2;
+}
+
 static __always_inline bool system_supports_fpsimd(void)
 {
 	return !cpus_have_const_cap(ARM64_HAS_NO_FPSIMD);
-- 
2.19.1