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Re: [PATCH v2 05/17] target/arm: Improve ID_AA64PFR0 FP/SIMD validation
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From: |
Richard Henderson |
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Subject: |
Re: [PATCH v2 05/17] target/arm: Improve ID_AA64PFR0 FP/SIMD validation |
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Date: |
Tue, 25 Feb 2020 07:55:44 -0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 |
On 2/25/20 5:24 AM, Peter Maydell wrote:
> This check is supposed to be "did the user accidentally specify
> some incompatible settings on their '-cpu,+this,-that' option?".
> By making it check the actual ID register values, you're turning
> it into also a check on "does the implementation specify sane
> ID register values", which (a) is useful for TCG but ought to
> be an assert and (b) we shouldn't be checking for KVM in case
> the h/w is giving us dubious ID values.
Hmm. Because kvm64 unconditionally set VFP and NEON, you're right. It was
only kvm32 that was examining id registers.
The only consequence of kvm giving us dubious id values that I can see is if
ADVSIMD is on, but FP is off, we won't migrate the register set.
Do you want me to add a tcg_enabled check, or shall we just drop the patch?
The existing test is good enough for just checking the command-line.
r~
- [PATCH v2 00/17] target/arm: vfp feature and decodetree cleanup, Richard Henderson, 2020/02/24
- [PATCH v2 02/17] target/arm: Rename isar_feature_aa32_fpdp_v2, Richard Henderson, 2020/02/24
- [PATCH v2 03/17] target/arm: Add isar_feature_aa32_{fpsp_v2, fpsp_v3, fpdp_v3}, Richard Henderson, 2020/02/24
- [PATCH v2 01/17] target/arm: Add isar_feature_aa32_vfp_simd, Richard Henderson, 2020/02/24
- [PATCH v2 05/17] target/arm: Improve ID_AA64PFR0 FP/SIMD validation, Richard Henderson, 2020/02/24
[PATCH v2 04/17] target/arm: Add isar_feature_aa64_fp_simd, isar_feature_aa32_vfp, Richard Henderson, 2020/02/24
[PATCH v2 07/17] target/arm: Replace ARM_FEATURE_VFP3 checks with fp{sp, dp}_v3, Richard Henderson, 2020/02/24
[PATCH v2 06/17] target/arm: Perform fpdp_v2 check first, Richard Henderson, 2020/02/24
[PATCH v2 08/17] target/arm: Add missing checks for fpsp_v2, Richard Henderson, 2020/02/24
[PATCH v2 09/17] target/arm: Replace ARM_FEATURE_VFP4 with isar_feature_aa32_simdfmac, Richard Henderson, 2020/02/24
[PATCH v2 10/17] target/arm: Remove ARM_FEATURE_VFP check from disas_vfp_insn, Richard Henderson, 2020/02/24