From: Andrew Murray <andrew.murray@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
Subject: [PATCH v1 1/3] arm64: cpufeature: Extract capped fields
Date: Fri, 25 Oct 2019 15:52:17 +0100 [thread overview]
Message-ID: <20191025145219.28350-2-andrew.murray@arm.com> (raw)
In-Reply-To: <20191025145219.28350-1-andrew.murray@arm.com>
When emulating ID registers there is often a need to cap the version
bits of a feature such that the guest will not use features that do
not yet exist.
Let's add a helper that extracts a field and caps the version to a
given value.
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
arch/arm64/include/asm/cpufeature.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 9cde5d2e768f..6b5bbf770969 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -447,6 +447,21 @@ cpuid_feature_extract_unsigned_field(u64 features, int field)
return cpuid_feature_extract_unsigned_field_width(features, field, 4);
}
+static inline u64 __attribute_const__
+cpuid_feature_cap_signed_field_width(u64 features, int field, int width,
+ s64 cap)
+{
+ s64 val = cpuid_feature_extract_signed_field_width(features, field,
+ width);
+
+ if (val > cap) {
+ features &= ~GENMASK_ULL(field + width - 1, field);
+ features |= cap << field;
+ }
+
+ return features;
+}
+
static inline u64 arm64_ftr_mask(const struct arm64_ftr_bits *ftrp)
{
return (u64)GENMASK(ftrp->shift + ftrp->width - 1, ftrp->shift);
--
2.21.0
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next prev parent reply other threads:[~2019-10-25 14:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 14:52 [PATCH v1 0/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters Andrew Murray
2019-10-25 14:52 ` Andrew Murray [this message]
2019-10-25 14:52 ` [PATCH v1 2/3] KVM: arm64: limit PMU version to ARMv8.4 Andrew Murray
2019-10-25 14:52 ` [PATCH v1 3/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters Andrew Murray
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