Re: [PATCH v3 00/11] Add TDX Guest Support (Initial support)

[Sathyanarayanan Kuppuswamy Natarajan]

Hi x86 maintainers,

On Fri, Jun 18, 2021 at 3:58 PM Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote:
>
> Hi All,
>
> Intel's Trust Domain Extensions (TDX) protect guest VMs from malicious
> hosts and some physical attacks. This series adds the basic TDX guest
> infrastructure support (including #VE handler support, and #VE support
> for halt and CPUID). This is just a subset of patches in the bare minimum
> TDX support patch list which is required for supporting minimal
> functional TDX guest. Other basic feature features like #VE support for
> IO, MMIO, boot optimization fixes and shared-mm support will be submitted
> in a separate patch set. To make reviewing easier we split it into smaller
> series. This series alone is not necessarily fully functional.
>
> Also, the host-side support patches, and support for advanced TD guest
> features like attestation or debug-mode will be submitted at a later time.
> Also, at this point it is not secure with some known holes in drivers, and
> also hasn’t been fully audited and fuzzed yet.
>
> TDX has a lot of similarities to SEV. It enhances confidentiality and
> of guest memory and state (like registers) and includes a new exception
> (#VE) for the same basic reasons as SEV-ES. Like SEV-SNP (not merged
> yet), TDX limits the host's ability to effect changes in the guest
> physical address space. With TDX the host cannot access the guest memory,
> so various functionality that would normally be done in KVM has moved
> into a (paravirtualized) guest. Partially this is done using the
> Virtualization Exception (#VE) and partially with direct paravirtual hooks.
>
> The TDX architecture also includes a new CPU mode called
> Secure-Arbitration Mode (SEAM). The software (TDX module) running in this
> mode arbitrates interactions between host and guest and implements many of
> the guarantees of the TDX architecture.
>
> Some of the key differences between TD and regular VM is,
>
> 1. Multi CPU bring-up is done using the ACPI MADT wake-up table.
> 2. A new #VE exception handler is added. The TDX module injects #VE exception
>    to the guest TD in cases of instructions that need to be emulated, disallowed
>    MSR accesses, etc.
> 3. By default memory is marked as private, and TD will selectively share it with
>    VMM based on need.
>
> Note that the kernel will also need to be hardened against low level inputs from
> the now untrusted hosts. This will be done in follow on patches.
>
> You can find TDX related documents in the following link.
>
> https://software.intel.com/content/www/br/pt/develop/articles/intel-trust-domain-extensions.html
>
> Changes since v1 (v2 is partial set submission):
>  * Patch titled "x86/x86: Add early_is_tdx_guest() interface" is moved
>    out of this series.
>  * Rest of the change log is added per patch.

I have submitted the following list of TDX patch series 2-3 weeks back, and so
far we only received feedback for a few patches in sets 1 and 4 (from Boris &
Tom Lendacky). So, I was curious if you were planning on taking a look at
other sets of patch series in this submission or were waiting for new
revisions? Please let me know your comments.

sets 1-4 are core sets of patches that add TDX guest support.
set 4+ adds extra TDX features support.

Add TDX Guest Support (Initial support) [set 1] (currently v3 version)
 - https://lore.kernel.org/patchwork/project/lkml/list/?series=505232

Add TDX Guest Support (#VE handler support) [set 2] (currently v2 version)
 - https://lore.kernel.org/patchwork/project/lkml/list/?series=506230

Add TDX Guest Support (boot fixes) [set 3] (currently v2 version)
 - https://lore.kernel.org/patchwork/project/lkml/list/?series=506231

Add TDX Guest Support (shared-mm support) [set 4] (currently v2 version)
 - https://lore.kernel.org/patchwork/project/lkml/list/?series=506232

Add TDX Guest Support (Debug support) [set 5] (currently v1 version)
 - https://lore.kernel.org/patchwork/project/lkml/list/?series=506233

Add TDX Guest Support (Attestation support) [set 6] (currently v1 version)
 - https://lore.kernel.org/patchwork/project/lkml/list/?series=506234


-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer