Re: [RFC v1 00/26] Add TDX Guest Support

[Kuppuswamy, Sathyanarayanan]

Hi All,

On 2/5/21 3:38 PM, Kuppuswamy Sathyanarayanan wrote:
> Hi All,
>
> NOTE: This series is not ready for wide public review. It is being
> specifically posted so that Peter Z and other experts on the entry
> code can look for problems with the new exception handler (#VE).
> That's also why x86@ is not being spammed.

We are currently working on a solution to fix the issues raised in
"Add #VE support for TDX guest" patch. While we fix that issue, I would
like to know if there are issues in other patches in this series. So if
possible can you please review other patches in the series and let us
know your comments?.

If you want me to rebase the series on top of v5.12-rcX kernel and repost it,
please let me know.

> Intel's Trust Domain Extensions (TDX) protect guest VMs from malicious
> hosts and some physical attacks. This series adds the bare-minimum
> support to run a TDX guest. The host-side support will be submitted
> separately. Also support for advanced TD guest features like attestation
> or debug-mode will be submitted separately. 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.
>
> In contrast to the SEV code in the kernel, TDX guest memory is integrity
> protected and isolated; the host is prevented from accessing guest
> memory (even ciphertext).
>
> 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, subset of CPUID leaves, etc.
> 3. By default memory is marked as private, and TD will selectively share it with
>     VMM based on need.
> 4. Remote attestation is supported to enable a third party (either the owner of
>     the workload or a user of the services provided by the workload) to establish
>     that the workload is running on an Intel-TDX-enabled platform located within a
>     TD prior to providing that workload data.
>
> 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
>
> This RFC series has been reviewed by Dave Hansen.
>
> Kirill A. Shutemov (16):
>    x86/paravirt: Introduce CONFIG_PARAVIRT_XL
>    x86/tdx: Get TD execution environment information via TDINFO
>    x86/traps: Add #VE support for TDX guest
>    x86/tdx: Add HLT support for TDX guest
>    x86/tdx: Wire up KVM hypercalls
>    x86/tdx: Add MSR support for TDX guest
>    x86/tdx: Handle CPUID via #VE
>    x86/io: Allow to override inX() and outX() implementation
>    x86/tdx: Handle port I/O
>    x86/tdx: Handle in-kernel MMIO
>    x86/mm: Move force_dma_unencrypted() to common code
>    x86/tdx: Exclude Shared bit from __PHYSICAL_MASK
>    x86/tdx: Make pages shared in ioremap()
>    x86/tdx: Add helper to do MapGPA TDVMALL
>    x86/tdx: Make DMA pages shared
>    x86/kvm: Use bounce buffers for TD guest
>
> Kuppuswamy Sathyanarayanan (6):
>    x86/cpufeatures: Add TDX Guest CPU feature
>    x86/cpufeatures: Add is_tdx_guest() interface
>    x86/tdx: Handle MWAIT, MONITOR and WBINVD
>    ACPI: tables: Add multiprocessor wake-up support
>    x86/topology: Disable CPU hotplug support for TDX platforms.
>    x86/tdx: Introduce INTEL_TDX_GUEST config option
>
> Sean Christopherson (4):
>    x86/boot: Add a trampoline for APs booting in 64-bit mode
>    x86/boot: Avoid #VE during compressed boot for TDX platforms
>    x86/boot: Avoid unnecessary #VE during boot process
>    x86/tdx: Forcefully disable legacy PIC for TDX guests
>
>   arch/x86/Kconfig                         |  28 +-
>   arch/x86/boot/compressed/Makefile        |   2 +
>   arch/x86/boot/compressed/head_64.S       |  10 +-
>   arch/x86/boot/compressed/misc.h          |   1 +
>   arch/x86/boot/compressed/pgtable.h       |   2 +-
>   arch/x86/boot/compressed/tdx.c           |  32 ++
>   arch/x86/boot/compressed/tdx_io.S        |   9 +
>   arch/x86/include/asm/apic.h              |   3 +
>   arch/x86/include/asm/asm-prototypes.h    |   1 +
>   arch/x86/include/asm/cpufeatures.h       |   1 +
>   arch/x86/include/asm/idtentry.h          |   4 +
>   arch/x86/include/asm/io.h                |  25 +-
>   arch/x86/include/asm/irqflags.h          |  42 +-
>   arch/x86/include/asm/kvm_para.h          |  21 +
>   arch/x86/include/asm/paravirt.h          |  22 +-
>   arch/x86/include/asm/paravirt_types.h    |   3 +-
>   arch/x86/include/asm/pgtable.h           |   3 +
>   arch/x86/include/asm/realmode.h          |   1 +
>   arch/x86/include/asm/tdx.h               | 114 +++++
>   arch/x86/kernel/Makefile                 |   1 +
>   arch/x86/kernel/acpi/boot.c              |  56 +++
>   arch/x86/kernel/apic/probe_32.c          |   8 +
>   arch/x86/kernel/apic/probe_64.c          |   8 +
>   arch/x86/kernel/head64.c                 |   3 +
>   arch/x86/kernel/head_64.S                |  13 +-
>   arch/x86/kernel/idt.c                    |   6 +
>   arch/x86/kernel/paravirt.c               |   4 +-
>   arch/x86/kernel/pci-swiotlb.c            |   2 +-
>   arch/x86/kernel/smpboot.c                |   5 +
>   arch/x86/kernel/tdx-kvm.c                | 116 +++++
>   arch/x86/kernel/tdx.c                    | 560 +++++++++++++++++++++++
>   arch/x86/kernel/tdx_io.S                 | 143 ++++++
>   arch/x86/kernel/topology.c               |   3 +-
>   arch/x86/kernel/traps.c                  |  73 ++-
>   arch/x86/mm/Makefile                     |   2 +
>   arch/x86/mm/ioremap.c                    |   8 +-
>   arch/x86/mm/mem_encrypt.c                |  74 ---
>   arch/x86/mm/mem_encrypt_common.c         |  83 ++++
>   arch/x86/mm/mem_encrypt_identity.c       |   1 +
>   arch/x86/mm/pat/set_memory.c             |  23 +-
>   arch/x86/realmode/rm/header.S            |   1 +
>   arch/x86/realmode/rm/trampoline_64.S     |  49 +-
>   arch/x86/realmode/rm/trampoline_common.S |   5 +-
>   drivers/acpi/tables.c                    |   9 +
>   include/acpi/actbl2.h                    |  21 +-
>   45 files changed, 1444 insertions(+), 157 deletions(-)
>   create mode 100644 arch/x86/boot/compressed/tdx.c
>   create mode 100644 arch/x86/boot/compressed/tdx_io.S
>   create mode 100644 arch/x86/include/asm/tdx.h
>   create mode 100644 arch/x86/kernel/tdx-kvm.c
>   create mode 100644 arch/x86/kernel/tdx.c
>   create mode 100644 arch/x86/kernel/tdx_io.S
>   create mode 100644 arch/x86/mm/mem_encrypt_common.c

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer