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Re: [Qemu-arm] [Qemu-devel] [PATCH v2 07/14] target/arm/cpu64: max cpu:
From: |
Richard Henderson |
Subject: |
Re: [Qemu-arm] [Qemu-devel] [PATCH v2 07/14] target/arm/cpu64: max cpu: Introduce sve<vl-bits> properties |
Date: |
Thu, 27 Jun 2019 18:19:57 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
On 6/27/19 5:16 PM, Dave Martin wrote:
> The architecture says:
>
> "For all purposes other than returning the result of a direct read of
> ZCR_EL1 then this field behaves as if it is set to the minimum of the
> stored value and the constrained length inherited from more privileged
> Exception levels in the current Security state, rounded down to the
> nearest implemented vector length."
>
> I think the behaviour of a direct read is implied: the LEN bits yielded
> by an MRS should contain exactly what was last written to them via MSR.
I agree.
Moreover, the value written to ZCR_ELx.LEN should not be directly adjusted
because the effective value also depends on ZCR_EL(x+1).LEN, and if the
higher-level EL register changes, the lower-level EL must see the effect.
The function that should be modified instead is sve_zcr_len_for_el().
r~
- Re: [Qemu-arm] [Qemu-devel] [PATCH v2 07/14] target/arm/cpu64: max cpu: Introduce sve<vl-bits> properties, (continued)
Re: [Qemu-arm] [PATCH v2 07/14] target/arm/cpu64: max cpu: Introduce sve<vl-bits> properties, Auger Eric, 2019/06/26
Re: [Qemu-arm] [PATCH v2 07/14] target/arm/cpu64: max cpu: Introduce sve<vl-bits> properties, Richard Henderson, 2019/06/27
[Qemu-arm] [PATCH v2 11/14] target/arm/kvm64: max cpu: Enable SVE when available, Andrew Jones, 2019/06/21
[Qemu-arm] [PATCH v2 12/14] target/arm/kvm: scratch vcpu: Preserve input kvm_vcpu_init features, Andrew Jones, 2019/06/21