Re: [PATCH RFC v7 40/64] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command

[Tom Lendacky]

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@xxxxxxx>
> > >
> > > 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@xxxxxxx>
> > > Signed-off-by: Harald Hoyer <harald@xxxxxxxxxxx>
> > > Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> > > Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> > > ---
> > >   .../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