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Subject: Re: [PATCH Part1 RFC v3 11/22] x86/sev: Add helper for validating
 pages in early enc attribute changes
To:     Borislav Petkov <bp@alien8.de>
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From:   Brijesh Singh <brijesh.singh@amd.com>
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Date:   Wed, 16 Jun 2021 09:36:19 -0500
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On 6/16/2021 8:10 AM, Brijesh Singh wrote:
> 
> On 6/16/21 8:02 AM, Borislav Petkov wrote:
>> On Wed, Jun 16, 2021 at 07:49:25AM -0500, Brijesh Singh wrote:
>>> If you still think ...
>> I think you should answer my question first:
>>
>>> Imagine you're a guest owner and you haven't written the SNP code and
>>> you don't know how it works.
>>>
>>> You start a guest in the public cloud and it fails because the
>>> hypervisor violates the GHCB protocol and all that guest prints before
>>> it dies is
>>>
>>> "general request termination"
>>>
>>> How are you - the guest owner - going to find out what exactly happened?
>>>
>>> Call support?
>> And let me paraphrase it again: if the error condition with which the
>> guest terminates is not uniquely identifiable but simply a "general
>> request", how are such conditions going to be debugged?
> > I thought I said it somewhere in our previous conversation, I would look
> at the KVM trace log, each vmgexit entry and exit are logged. The log
> contains full GHCB MSR value, and in it you can see both the request and
> response code and decode the failure reason.
> 

I now realized that in this case we may not have the trace's. It's
a production environment and my development machine :(. I will go ahead and
add the error message when guest sees an invalid response code before
terminating it. Will do the similar error message in the decompression
path.

-Brijesh