linux-kernel - Re: [PATCH v2 3/5] virt: sevguest: Prep for kernel internal {get, get_ext}

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Date:   Tue, 15 Aug 2023 15:11:23 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Dionna Amalie Glaze <dionnaglaze@...gle.com>
Cc:     linux-coco@...ts.linux.dev, Borislav Petkov <bp@...en8.de>,
        Brijesh Singh <brijesh.singh@....com>, peterz@...radead.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] virt: sevguest: Prep for kernel internal {get,
 get_ext}_report()

On 8/14/23 18:24, Dan Williams wrote:
> Dionna Amalie Glaze wrote:
>>>
>>>          switch (ioctl) {
>>>          case SNP_GET_REPORT:
>>> -               ret = get_report(snp_dev, &input);
>>> +               ret = get_report(snp_dev, &input, SNP_UARG);
>>>                  break;
>>>          case SNP_GET_DERIVED_KEY:
>>>                  ret = get_derived_key(snp_dev, &input);
>>>                  break;
>>
>> Do we have an agreement around the continued existence of sev-guest
>> for supporting derived keys, is that similarly slated for the chopping
>> block, or is it left undecided?
>> It appears your choice to not include the uarg/karg extension here is
>> deliberate.
> 
> I do want to understand the argument from James a bit more, but the
> exlcusion here was simply because there is currently no support for this
> concept from other vendors.
> 
> That said, if it remains a vendor unique concept and continues getting
> suspicious looks from folks like James, it may indeed be something the
> kernel wants to jettison.

I'm not sure why we would want to jettison it. Just because other vendors 
don't have a key derivation function doesn't mean it can't be useful to 
customers that want to use it on AMD platforms.

Thanks,
Tom

> 
>>>          case SNP_GET_EXT_REPORT:
>>> -               ret = get_ext_report(snp_dev, &input);
>>> +               ret = get_ext_report(snp_dev, &input, SNP_UARG);
>>>                  break;
>>>          default:
>>>                  break;
>>>
>>
>> Reviewed-by: Dionna Glaze <dionnaglaze@...gle.com>
> 
> Thanks for all your help on this!