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Re: [RFC PATCH] target/arm: properly document FEAT_CRC32
From: |
Alex Bennée |
Subject: |
Re: [RFC PATCH] target/arm: properly document FEAT_CRC32 |
Date: |
Fri, 24 Feb 2023 15:27:50 +0000 |
User-agent: |
mu4e 1.9.21; emacs 29.0.60 |
Peter Maydell <peter.maydell@linaro.org> writes:
> On Thu, 23 Feb 2023 at 23:01, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> On 2/22/23 01:01, Alex Bennée wrote:
>> > This is a mandatory feature for Armv8.1 architectures but we don't
>> > state the feature clearly in our emulation list. While checking verify
>> > our cortex-a76 model matches up with the current TRM by breaking out
>> > the long form isar into a more modern readable FIELD_DP code.
>> >
>> > Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> > ---
>> > docs/system/arm/emulation.rst | 1 +
>> > target/arm/cpu64.c | 29 ++++++++++++++++++++++++++---
>> > target/arm/cpu_tcg.c | 2 +-
>> > 3 files changed, 28 insertions(+), 4 deletions(-)
>> >
>> > diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
>> > index 2062d71261..2c4fde5eef 100644
>> > --- a/docs/system/arm/emulation.rst
>> > +++ b/docs/system/arm/emulation.rst
>> > @@ -14,6 +14,7 @@ the following architecture extensions:
>> > - FEAT_BBM at level 2 (Translation table break-before-make levels)
>> > - FEAT_BF16 (AArch64 BFloat16 instructions)
>> > - FEAT_BTI (Branch Target Identification)
>> > +- FEAT_CRC32 (CRC32 instruction)
>> > - FEAT_CSV2 (Cache speculation variant 2)
>> > - FEAT_CSV2_1p1 (Cache speculation variant 2, version 1.1)
>> > - FEAT_CSV2_1p2 (Cache speculation variant 2, version 1.2)
>> > diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
>> > index 4066950da1..12e1a532ab 100644
>> > --- a/target/arm/cpu64.c
>> > +++ b/target/arm/cpu64.c
>> > @@ -912,6 +912,8 @@ static void aarch64_a72_initfn(Object *obj)
>> > static void aarch64_a76_initfn(Object *obj)
>> > {
>> > ARMCPU *cpu = ARM_CPU(obj);
>> > + uint64_t t;
>> > + uint32_t u;
>> >
>> > cpu->dtb_compatible = "arm,cortex-a76";
>> > set_feature(&cpu->env, ARM_FEATURE_V8);
>> > @@ -928,7 +930,18 @@ static void aarch64_a76_initfn(Object *obj)
>> > cpu->ctr = 0x8444C004;
>> > cpu->dcz_blocksize = 4;
>> > cpu->isar.id_aa64dfr0 = 0x0000000010305408ull;
>> > - cpu->isar.id_aa64isar0 = 0x0000100010211120ull;
>> > +
>> > + /* per r4p1 of the Cryptographic Extension TRM */
>> > + t = cpu->isar.id_aa64isar0;
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, AES, 2); /* FEAT_PMULL */
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, SHA1, 1); /* FEAT_SHA1 */
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, SHA2, 1); /* FEAT_SHA512 */
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, CRC32, 1); /* FEAT_CRC32 */
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, ATOMIC, 2); /* FEAT_LSE */
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, RDM, 1); /* FEAT_RDM */
>> > + t = FIELD_DP64(t, ID_AA64ISAR0, DP, 1); /* FEAT_DotProd */
>> > + cpu->isar.id_aa64isar0 = t;
>>
>> Ok, so, this might be helpful for grepping, but it's not helpful for reading
>> the
>> documentation, which on page B2-137 uses hex.
>
> Agreed -- we write these functions and review them by looking
> at the TRMs, and the TRMs specify the values of the ID registers
> as straight hex values.
Ahh found it now was confusing the pages with sections: B2.4 on page
B2-137.
>
> thanks
> -- PMM
--
Alex Bennée
Virtualisation Tech Lead @ Linaro