linux-kernel - Re: [PATCH v5 03/22] KVM: arm64: Support SDEI

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Message-ID: <09814baf-3107-5fa9-f92c-cc271f384c4a@redhat.com>
Date:   Fri, 25 Mar 2022 14:11:11 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Oliver Upton <oupton@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, maz@...nel.org,
        linux-kernel@...r.kernel.org, eauger@...hat.com,
        shan.gavin@...il.com, Jonathan.Cameron@...wei.com,
        pbonzini@...hat.com, vkuznets@...hat.com, will@...nel.org
Subject: Re: [PATCH v5 03/22] KVM: arm64: Support SDEI_VERSION hypercall

Hi Oliver,

On 3/24/22 3:48 PM, Oliver Upton wrote:
> On Thu, Mar 24, 2022 at 12:07:34PM +0800, Gavin Shan wrote:
> 
> [...]
> 
>>>> Yeah, I was sticky to the pattern of "KVM". However, I think it's good
>>>> to reuse the existing one. Lets use ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2
>>>> if you agree. Its first two characters are "VM" at least.
>>>
>>> Sounds fine to me. The only other nit I'd say is we should define a
>>> macro for it too, something like:
>>>
>>>     #define KVM_SDEI_VENDOR	ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2
>>>
>>
>> Agreed, and the macro will be put into arch/arm64/include/asm/kvm_sdei.h.
>> arch/arm64/include/uapi/asm/kvm_sdei_state.h isn't the right place because
>> the dependent macro ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2 isn't exposed by
>> ABI.
> 
> The argument could definitely be made that our vendor ID should be
> promoted to UAPI. Even though linux is the only known user of our
> vendor-specific hypercalls, nothing is stopping other software from
> using them. Beyond that, these values should really never change anyway.
> 
> It isn't a big deal if you add it to internal headers, either, as the
> only known consumer will be the kernel.
> 

Sure. Lets add it into include/asm/kvm_sdei.h in next respin. We can
expose it when it is needed. For now, I do think Linux is the only
user.

Thanks,
Gavin