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arm64: Support systems without FP/ASIMD

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The arm64 kernel assumes that FP/ASIMD units are always present
and accesses the FP/ASIMD specific registers unconditionally. This
could cause problems when they are absent. This patch adds the
support for kernel handling systems without FP/ASIMD by skipping the
register access within the kernel. For kvm, we trap the accesses
to FP/ASIMD and inject an undefined instruction exception to the VM.

The callers of the exported kernel_neon_begin_partial() should
make sure that the FP/ASIMD is supported.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
[catalin.marinas@arm.com: add comment on the ARM64_HAS_NO_FPSIMD conflict and the new location]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Suzuki K Poulose
2016-11-08 13:56:21 +00:00
committed by Catalin Marinas
parent a4023f6827
commit 82e0191a1a
7 changed files with 65 additions and 4 deletions
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15
arch/arm64/kernel/cpufeature.c
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@@ -746,6 +746,14 @@ static bool hyp_offset_low(const struct arm64_cpu_capabilities *entry,
return idmap_addr > GENMASK(VA_BITS - 2, 0) && !is_kernel_in_hyp_mode();
}
static bool has_no_fpsimd(const struct arm64_cpu_capabilities *entry, int __unused)
{
u64 pfr0 = read_system_reg(SYS_ID_AA64PFR0_EL1);
return cpuid_feature_extract_signed_field(pfr0,
ID_AA64PFR0_FP_SHIFT) < 0;
}
static const struct arm64_cpu_capabilities arm64_features[] = {
{
.desc = "GIC system register CPU interface",
@@ -829,6 +837,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.def_scope = SCOPE_SYSTEM,
.matches = hyp_offset_low,
},
{
/* FP/SIMD is not implemented */
.capability = ARM64_HAS_NO_FPSIMD,
.def_scope = SCOPE_SYSTEM,
.min_field_value = 0,
.matches = has_no_fpsimd,
},
{},
};