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SubjectRe: [RFC PATCH 00/35] SEV-ES hypervisor support
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On 9/14/20 5:59 PM, Sean Christopherson wrote:
> On Mon, Sep 14, 2020 at 03:15:14PM -0500, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>
>> This patch series provides support for running SEV-ES guests under KVM.
>
> From the x86/VMX side of things, the GPR hooks are the only changes that I
> strongly dislike.
>
> For the vmsa_encrypted flag and related things like allow_debug(), I'd
> really like to aim for a common implementation between SEV-ES and TDX[*] from
> the get go, within reason obviously. From a code perspective, I don't think
> it will be too onerous as the basic tenets are quite similar, e.g. guest
> state is off limits, FPU state is autoswitched, etc..., but I suspect (or
> maybe worry?) that there are enough minor differences that we'll want a more
> generic way of marking ioctls() as disallowed to avoid having one-off checks
> all over the place.
>
> That being said, it may also be that there are some ioctls() that should be
> disallowed under SEV-ES, but aren't in this series. E.g. I assume
> kvm_vcpu_ioctl_smi() should be rejected as KVM can't do the necessary
> emulation (I assume this applies to vanilla SEV as well?).

Right, SMM isn't currently supported under SEV-ES. SEV does support SMM,
though, since the register state can be altered to change over to the SMM
register state. So the SMI ioctl() is ok for SEV.

>
> One thought to try and reconcile the differences between SEV-ES and TDX would
> be expicitly list which ioctls() are and aren't supported and go from there?
> E.g. if there is 95% overlap than we probably don't need to get fancy with
> generic allow/deny.
>
> Given that we don't yet have publicly available KVM code for TDX, what if I
> generate and post a list of ioctls() that are denied by either SEV-ES or TDX,
> organized by the denier(s)? Then for the ioctls() that are denied by one and
> not the other, we add a brief explanation of why it's denied?
>
> If that sounds ok, I'll get the list and the TDX side of things posted
> tomorrow.

That sounds good.

Thanks,
Tom

>
> Thanks!
>
>
> [*] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsoftware.intel.com%2Fcontent%2Fwww%2Fus%2Fen%2Fdevelop%2Farticles%2Fintel-trust-domain-extensions.html&amp;data=02%7C01%7Cthomas.lendacky%40amd.com%7C000b3d355429471694fa08d85901e575%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637357211966578452&amp;sdata=nEhXcrxY7KmQVCsVJrX20bagZLbzwVqlT%2BYvhSYCjHI%3D&amp;reserved=0
>

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