linux-kernel - Re: [PATCH RFC v7 40/64] KVM: SVM: Add KVM_SEV_SNP_LAUNCH

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Date:   Tue, 20 Dec 2022 08:25:34 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     "Kalra, Ashish" <ashish.kalra@....com>,
        Michael Roth <michael.roth@....com>, kvm@...r.kernel.org
Cc:     linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, hpa@...or.com, ardb@...nel.org,
        pbonzini@...hat.com, seanjc@...gle.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
        peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
        rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
        bp@...en8.de, vbabka@...e.cz, kirill@...temov.name,
        ak@...ux.intel.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        dgilbert@...hat.com, jarkko@...nel.org, harald@...fian.com,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH RFC v7 40/64] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH
 command

On 12/19/22 17:24, Kalra, Ashish wrote:
> Hello Tom,
> 
> On 12/19/2022 12:04 PM, Tom Lendacky wrote:
>> On 12/14/22 13:40, Michael Roth wrote:
>>> From: Brijesh Singh <brijesh.singh@....com>
>>>
>>> The KVM_SEV_SNP_LAUNCH_FINISH finalize the cryptographic digest and stores
>>> it as the measurement of the guest at launch.
>>>
>>> While finalizing the launch flow, it also issues the LAUNCH_UPDATE command
>>> to encrypt the VMSA pages.
>>>
>>> If its an SNP guest, then VMSA was added in the RMP entry as
>>> a guest owned page and also removed from the kernel direct map
>>> so flush it later after it is transitioned back to hypervisor
>>> state and restored in the direct map.
>>>
>>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>>> Signed-off-by: Harald Hoyer <harald@...fian.com>
>>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>>> Signed-off-by: Michael Roth <michael.roth@....com>
>>> ---
>>>   .../virt/kvm/x86/amd-memory-encryption.rst    |  22 ++++
>>>   arch/x86/kvm/svm/sev.c                        | 119 ++++++++++++++++++
>>>   include/uapi/linux/kvm.h                      |  14 +++
>>>   3 files changed, 155 insertions(+)
>>>
>>> diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst 
>>> b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
>>> index c94be8e6d657..e4b42aaab1de 100644
>>> --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
>>> +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
>>> @@ -513,6 +513,28 @@ Returns: 0 on success, -negative on error
>>>   See the SEV-SNP spec for further details on how to build the VMPL 
>>> permission
>>>   mask and page type.
>>> +21. KVM_SNP_LAUNCH_FINISH
>>> +-------------------------
>>> +
>>> +After completion of the SNP guest launch flow, the 
>>> KVM_SNP_LAUNCH_FINISH command can be
>>> +issued to make the guest ready for the execution.
>>> +
>>> +Parameters (in): struct kvm_sev_snp_launch_finish
>>> +
>>> +Returns: 0 on success, -negative on error
>>> +
>>> +::
>>> +
>>> +        struct kvm_sev_snp_launch_finish {
>>> +                __u64 id_block_uaddr;
>>> +                __u64 id_auth_uaddr;
>>> +                __u8 id_block_en;
>>> +                __u8 auth_key_en;
>>> +                __u8 host_data[32];
>>
>> This is missing the 6 bytes of padding at the end of the struct.
>>
> 
> Yes will fix this, the documentation is missing that, the structure 
> defination in include/uapi/linux/kvm.h includes it.
> 
> But why do we need this padding ?
> 

I'm assuming it was added so that any new elements added would be aligned 
on an 8 byte boundary (should the next element added be a __u64). I don't 
think that it is truly needed right now, though.

Thanks,
Tom