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SubjectRe: [PATCH RFC v7 40/64] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command
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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@amd.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@amd.com>
>>> Signed-off-by: Harald Hoyer <harald@profian.com>
>>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>>> Signed-off-by: Michael Roth <michael.roth@amd.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

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