linux-kernel - Re: [PATCH v6 04/18] KVM: arm64: Support SDEI_EVENT

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Message-ID: <a6122234-907a-4ede-26fc-872c196c5912@redhat.com>
Date:   Mon, 2 May 2022 15:28:24 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Oliver Upton <oupton@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        eauger@...hat.com, Jonathan.Cameron@...wei.com,
        vkuznets@...hat.com, will@...nel.org, shannon.zhaosl@...il.com,
        james.morse@....com, mark.rutland@....com, maz@...nel.org,
        pbonzini@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH v6 04/18] KVM: arm64: Support SDEI_EVENT_REGISTER
 hypercall

Hi Oliver,

On 5/2/22 11:43 AM, Oliver Upton wrote:
> On Mon, May 02, 2022 at 10:55:51AM +0800, Gavin Shan wrote:
>>>> +	unsigned long route_mode = smccc_get_arg(vcpu, 4);
>>>
>>> This is really 'flags'. route_mode is bit[0]. I imagine we don't want to
>>> support relative mode, so bit[1] is useless for us in that case too.
>>>
>>> The spec is somewhat imprecise on what happens for reserved flags. The
>>> prototype in section 5.1.2 of [1] suggests that reserved bits must be
>>> zero, but 5.1.2.3 'Client responsibilities' does not state that invalid
>>> flags result in an error.
>>>
>>> Arm TF certainly rejects unexpected flags [2].
>>>
>>> [1]: DEN0054C https://developer.arm.com/documentation/den0054/latest
>>> [2]: https://github.com/ARM-software/arm-trusted-firmware/blob/66c3906e4c32d675eb06bd081de8a3359f76b84c/services/std_svc/sdei/sdei_main.c#L260
>>>
>>
>> Yes, This chunk of code is still stick to old specification. Lets
>> improve in next respin:
>>
>>     - Rename @route_mode to @flags
>>     - Reject if the reserved bits are set.
>>     - Reject if relative mode (bit#1) is selected.
>>     - Reject if routing mode (bit#0) isn't RM_ANY (0).
> 
> Bit[0] is ignored for private events, actually. So we really just reject
> if any of bit[63:1] are set.
> 

It makes sense to me. Thanks for your confirm :)

Thanks,
Gavin