Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver

[Kai Huang <kai.huang@intel.com>]

On Fri, 2022-04-15 at 15:01 -0700, Kuppuswamy Sathyanarayanan wrote:
> --- /dev/null
> +++ b/drivers/platform/x86/intel/tdx/Kconfig
> @@ -0,0 +1,13 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# X86 TDX Platform Specific Drivers
> +#
> +
> +config INTEL_TDX_ATTESTATION
> +	tristate "Intel TDX attestation driver"
> +	depends on INTEL_TDX_GUEST
> +	help
> +	  The TDX attestation driver provides IOCTL interfaces to the user to
> +	  request TDREPORT from the TDX module or request quote from the VMM
> +	  or to get quote buffer size. It is mainly used to get secure disk
> +	  decryption keys from the key server.
> diff --git a/drivers/platform/x86/intel/tdx/Makefile b/drivers/platform/x86/intel/tdx/Makefile
> new file mode 100644
> index 000000000000..94eea6108fbd
> --- /dev/null
> +++ b/drivers/platform/x86/intel/tdx/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_INTEL_TDX_ATTESTATION)	+= intel_tdx_attest.o
> diff --git a/drivers/platform/x86/intel/tdx/intel_tdx_attest.c b/drivers/platform/x86/intel/tdx/intel_tdx_attest.c
> new file mode 100644
> index 000000000000..9124db800d4f
> --- /dev/null
> +++ b/drivers/platform/x86/intel/tdx/intel_tdx_attest.c


From security's perspective, attestation is an essential part of TDX.  That
being said, w/o attestation support in TD guest, I guess nobody will seriously
use TD guest.

From this perspective, I am not sure what's the value of having a dedicated
INTEL_TDX_ATTESTATION Kconfig.  The attestation support code should be turned on
unconditionally when CONFIG_INTEL_TDX_GUEST is on.  The code can also be just
under arch/x86/coco/tdx/ I guess?

But I'll leave this to maintainers.