[PATCH v5 1/3] arm64: cpufeature: Extract capped fields
From: Andrew Murray <hidden>
Date: 2020-01-27 11:45:08
Also in:
kvmarm
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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 <redacted> --- arch/arm64/include/asm/cpufeature.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 4261d55..1462fd1 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h@@ -447,6 +447,22 @@ 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); + u64 mask = GENMASK_ULL(field + width - 1, field); + + if (val > cap) { + features &= ~mask; + features |= (cap << field) & mask; + } + + return features; +} + static inline u64 arm64_ftr_mask(const struct arm64_ftr_bits *ftrp) { return (u64)GENMASK(ftrp->shift + ftrp->width - 1, ftrp->shift);
--
2.7.4
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