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    Subject[PATCH v9 0/6] Add TDX Guest Attestation support
    Date
    Hi All,

    Intel's Trust Domain Extensions (TDX) protect guest VMs from malicious
    hosts and some physical attacks. VM guest with TDX support is called
    as TD Guest.

    In TD Guest, the attestation process is used to verify the
    trustworthiness of TD guest to the 3rd party servers. Such attestation
    process is required by 3rd party servers before sending sensitive
    information to TD guests. One usage example is to get encryption keys
    from the key server for mounting the encrypted rootfs or secondary drive.

    During TD launch, the initial contents and configuration of the TD are
    recorded by the Intel TDX module in the build time measurement register
    (MRTD). In addition, run-time measurement registers (RTMRs) can be
    used by the guest TD software, e.g., to measure a boot process. At
    run-time, the Intel TDX module reuses the Intel SGX attestation
    infrastructure to provide support for attesting to these measurements
    as described below.

    Intel TDX attestation is intended to be used in two phases:

    TD Guest can use the TDCALL(TDG.MR.REPORT) function to request the
    Intel TDX Module to generate an integrity-protected TDREPORT structure
    (TDREPORT_STRUCT). This structure includes the TD’s measurements, the
    Intel TDX module’s measurements, and a value provided by the guest TD
    software. This will typically be an asymmetric key that the attestation
    verifier can use to establish a secure channel or protect sensitive
    data to be sent to the TD software.

    To protect the integrity of TDREPORT_STRUCT, it is HMAC'ed using an
    HMAC key which by design can only be verified on the local platform via
    the SGX ENCLU(EVERIFYREPORT2) instruction. So to create a remotely
    verifiable attestation, the TDREPORT_STRUCT should be converted into a
    Quote signed by a certified Quote signing key.

    An Intel SGX Quoting Enclave (QE), written specifically to support
    quoting Intel TDX TDs, uses EVERIFYREPORT2, to help check the integrity
    of the TDG.MR.REPORT. If it passes, the QE can use a certified quote
    signing key to sign a quote containing the guest TD’s measurements and
    the additional data being quoted.

    Method of sending the TDREPORT to QE and to get the Quote depends on
    the implementation and deployment of QE. For quote requests from the
    guest user space, communication models like vsock or TCP/IP can be
    used to get the Quote from QE. But for requests generated during
    pre-boot time, since such communication methods may not be available,
    QEs at basic had to support GetQuote hypercall model. To keep the
    attestation communication protocol same during pre-boot and
    post-boot time, some QEs may just opt only to support GetQuote
    hypercall request model. So add support to allow guest TD user space
    get the Quote using GetQuote hypercall.

    Since the Quote generation involves communication with QE, the response
    time cannot be accurately defined and is generally long. So to let the TD
    guest not wait for the response, host VMM supports callback event
    notification via an interrupt vector. This can be used by the host to
    notify the TD regarding the completion of the Quote request.

    Following patches add the attestation support to the TDX guest which
    includes attestation user interface driver, related hypercall
    support and self test modules.

    Patch 1-2/6 -> Adds TDREPORT support and related selftest.
    Patch 3/6 -> Adds event notification IRQ support
    Patch 4/6 -> Adds cc_decrypted_alloc/free() support
    Patch 5-6/6 -> Adds Quote generation support and related selftest.

    Any distribution enabling TDX is also expected to need attestation. So
    enable it by default with TDX guest support. The compiled size is
    quite small (~500 bytes).

    Changes since v8:
    * To keep the interface generic to TDX guest, changed interface device
    name from tdx-attest -> tdx-guest. Also moved interface device creation
    logic from attest.c -> tdx.c.
    * Converted test app into self test module as per review suggestion.
    * Added subtype and length parameters to tdx_report_req ABI.
    * Regarding event notification IRQ, changed static IRQ vector
    reservation to runtime model.
    * For quote generation shared buffer allocation, replace vmap based
    allocation with DMA wrappers (cc_decrypted_alloc/free()).
    * Fixed commit log as per review comments.

    Changes since v7:
    * Removed exports symbols for tdx_setup_ev_notify_handler() and
    tdx_remove_ev_notify_handler().
    * Changed "struct quote_buf *buf" member in "struct quote_entry"
    from pointer to embed object.
    * Rebased on top of v5.19-rc1.

    Changes since v6:
    * Fixed race between wait_for_completion_*() and
    quote_callback_handler() in tdx_get_quote() when user terminates the
    request.
    * Fixed commit log and comments.

    Changes since v5:
    * Added support for parallel GetQuote requests.
    * Add noalias variants of set_memory_*crypted() functions to
    changes page attribute without touching direct map.
    * Made set_memory_*crypted() functions vmalloc address compatible.
    * Use vmap()/set_memory_*crypted() functions to share/unshare
    memory without touching the direct map.
    * Add support to let driver handle the memory cleanup for the
    early termination of user requests.
    * Removed unused headers in attest.c
    * Fixed commit log and comments as per review comments.

    Changes since v4:
    * Removed platform driver model in attestation driver and used
    miscdevice and initcall approach.
    * Since dma_alloc*() APIs require a valid device reference,
    replaced it with __get_free_pages() and set_memory_decrypted()
    for quote memory allocation.
    * Removed tdx_mcall_tdreport() and moved TDG.MR.REPORT TDCALL code
    to tdx_get_report().
    * Used kmalloc() for TDREPORT memory allocation instead of
    get_zeroed_page().
    * Returned -EINVAL in default case of tdx_attest_ioctl().
    * Added struct tdx_report_req to explicitly mention the
    TDX_CMD_GET_REPORT IOCTL argument.
    * Removed tdx_get_quote_hypercall() and moved hypercall code to
    attestation driver itself.
    * Removed GetQuote timeout support (since it is not defined in
    spec)
    * Added support to check for spurious callback interrupt in GetQuote
    request.
    * Fixed commit log and comments as per review suggestions.


    Changes since v3:
    * Moved the attestation driver from platform/x86 to arch/x86/coco/tdx/ and
    renamed intel_tdx_attest.c to attest.c.
    * Dropped CONFIG_INTEL_TDX_ATTESTATION and added support to compile
    attestation changes with CONFIG_INTEL_TDX_GUEST option.
    * Merged patch titled "x86/tdx: Add tdx_mcall_tdreport() API support" and
    "platform/x86: intel_tdx_attest: Add TDX Guest attestation interface" into
    a single patch.
    * Moved GetQuote IOCTL support changes from patch titled "platform/x86:
    intel_tdx_attest: Add TDX Guest attestation interface driver" to a
    separate patch.
    * Removed 8K size restriction when requesting quote, and added support
    to let userspace decide the quote size.
    * Added support to allow attestation agent configure quote generation
    timeout value.
    * Fixed commit log and comments as per review comments.

    Changes since v2:
    * As per Han's suggestion, modified the attestation driver to use
    platform device driver model.
    * Modified tdx_hcall_get_quote() and tdx_mcall_tdreport() APIs to
    return TDCALL error code instead of generic error info (like -EIO).
    * Removed attestation test app patch from this series to simplify
    the patchset and review process. Test app patches will be submitted
    once attestation support patches are merged.
    * Since patches titled "x86/tdx: Add SetupEventNotifyInterrupt TDX
    hypercall support" and "x86/tdx: Add TDX Guest event notify
    interrupt vector support" are related, combining them into a
    single patch.

    Changes since v1:
    * Moved test driver from "tools/tdx/attest/tdx-attest-test.c" to
    "tools/arch/x86/tdx/attest/tdx-attest-test.c" as per Hans review
    suggestion.
    * Minor commit log and comment fixes in patches titled
    "x86/tdx: Add tdx_mcall_tdreport() API support" and "x86/tdx:
    Add tdx_hcall_get_quote() API support"
    * Extended tdx_hcall_get_quote() API to accept GPA length as argument
    to accomodate latest TDQUOTE TDVMCALL related specification update.
    * Added support for tdx_setup_ev_notify_handler() and
    tdx_remove_ev_notify_handler() in patch titled "x86/tdx: Add TDX
    Guest event notify interrupt vector support"


    Kuppuswamy Sathyanarayanan (6):
    x86/tdx: Add TDX Guest attestation interface driver
    selftests: tdx: Test GetReport TDX attestation feature
    x86/tdx: Add TDX Guest event notify interrupt support
    x86/coco: Add cc_decrypted_alloc/free() interfaces
    x86/tdx: Add Quote generation support
    selftests: tdx: Test GetQuote TDX attestation feature

    arch/x86/coco/Makefile | 2 +-
    arch/x86/coco/mem.c | 90 +++++
    arch/x86/coco/tdx/Makefile | 2 +-
    arch/x86/coco/tdx/attest.c | 363 ++++++++++++++++++
    arch/x86/coco/tdx/tdx.c | 149 +++++++
    arch/x86/coco/tdx/tdx.h | 11 +
    arch/x86/include/asm/coco.h | 10 +
    arch/x86/include/asm/tdx.h | 2 +
    arch/x86/include/uapi/asm/tdx.h | 96 +++++
    tools/testing/selftests/Makefile | 1 +
    tools/testing/selftests/tdx/Makefile | 7 +
    tools/testing/selftests/tdx/tdx_attest_test.c | 214 +++++++++++
    12 files changed, 945 insertions(+), 2 deletions(-)
    create mode 100644 arch/x86/coco/mem.c
    create mode 100644 arch/x86/coco/tdx/attest.c
    create mode 100644 arch/x86/coco/tdx/tdx.h
    create mode 100644 arch/x86/include/uapi/asm/tdx.h
    create mode 100644 tools/testing/selftests/tdx/Makefile
    create mode 100644 tools/testing/selftests/tdx/tdx_attest_test.c

    --
    2.25.1

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