linux-kernel - Re: [PATCH] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

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Date:   Mon, 21 Mar 2022 18:08:38 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     kvm list <kvm@...r.kernel.org>, Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <jroedel@...e.de>, Marc Orr <marcorr@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

On 3/21/22 16:42, Peter Gonda wrote:
> On Mon, Mar 21, 2022 at 9:27 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>>
>> On 3/21/22 16:02, Peter Gonda wrote:
>>> SEV-ES guests can request termination using the GHCB's MSR protocol. See
>>> AMD's GHCB spec section '4.1.13 Termination Request'. Currently when a
>>> guest does this the userspace VMM sees an KVM_EXIT_UNKNOWN (-EVINAL)
>>> return code from KVM_RUN. By adding a KVM_EXIT_SHUTDOWN_ENTRY to kvm_run
>>> struct the userspace VMM can clearly see the guest has requested a SEV-ES
>>> termination including the termination reason code set and reason code.
>>>
>>> Signed-off-by: Peter Gonda <pgonda@...gle.com>
>>> Cc: Borislav Petkov <bp@...en8.de>
>>> Cc: Tom Lendacky <thomas.lendacky@....com>
>>> Cc: Brijesh Singh <brijesh.singh@....com>
>>> Cc: Joerg Roedel <jroedel@...e.de>
>>> Cc: Marc Orr <marcorr@...gle.com>
>>> Cc: Sean Christopherson <seanjc@...gle.com>
>>> Cc: kvm@...r.kernel.org
>>> Cc: linux-kernel@...r.kernel.org
>>
>> Looks good, but it has to also add a capability.
> 
> Thanks for the quick review! Just so I understand. I should add
> KVM_CAP_SEV_TERM or something, then if that has been enabled do the
> new functionality, else keep the old functionality?

No, much simpler; just something for which KVM_CHECK_EXTENSION returns 
1, so that userspace knows that there is a "shutdown" member to be 
filled by KVM_EXIT_SHUTDOWN.  e.g. KVM_CAP_EXIT_SHUTDOWN_REASON.

Paolo