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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /Documentation/virt/coco
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
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Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/virt/coco')
-rw-r--r--Documentation/virt/coco/sev-guest.rst161
-rw-r--r--Documentation/virt/coco/tdx-guest.rst52
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diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+The Definitive SEV Guest API Documentation
+===================================================================
+
+1. General description
+======================
+
+The SEV API is a set of ioctls that are used by the guest or hypervisor
+to get or set a certain aspect of the SEV virtual machine. The ioctls belong
+to the following classes:
+
+ - Hypervisor ioctls: These query and set global attributes which affect the
+ whole SEV firmware. These ioctl are used by platform provisioning tools.
+
+ - Guest ioctls: These query and set attributes of the SEV virtual machine.
+
+2. API description
+==================
+
+This section describes ioctls that is used for querying the SEV guest report
+from the SEV firmware. For each ioctl, the following information is provided
+along with a description:
+
+ Technology:
+ which SEV technology provides this ioctl. SEV, SEV-ES, SEV-SNP or all.
+
+ Type:
+ hypervisor or guest. The ioctl can be used inside the guest or the
+ hypervisor.
+
+ Parameters:
+ what parameters are accepted by the ioctl.
+
+ Returns:
+ the return value. General error numbers (-ENOMEM, -EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+The guest ioctl should be issued on a file descriptor of the /dev/sev-guest
+device. The ioctl accepts struct snp_user_guest_request. The input and
+output structure is specified through the req_data and resp_data field
+respectively. If the ioctl fails to execute due to a firmware error, then
+the fw_error code will be set, otherwise fw_error will be set to -1.
+
+The firmware checks that the message sequence counter is one greater than
+the guests message sequence counter. If guest driver fails to increment message
+counter (e.g. counter overflow), then -EIO will be returned.
+
+::
+
+ struct snp_guest_request_ioctl {
+ /* Message version number */
+ __u32 msg_version;
+
+ /* Request and response structure address */
+ __u64 req_data;
+ __u64 resp_data;
+
+ /* bits[63:32]: VMM error code, bits[31:0] firmware error code (see psp-sev.h) */
+ union {
+ __u64 exitinfo2;
+ struct {
+ __u32 fw_error;
+ __u32 vmm_error;
+ };
+ };
+ };
+
+2.1 SNP_GET_REPORT
+------------------
+
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in): struct snp_report_req
+:Returns (out): struct snp_report_resp on success, -negative on error
+
+The SNP_GET_REPORT ioctl can be used to query the attestation report from the
+SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
+provided by the SEV-SNP firmware to query the attestation report.
+
+On success, the snp_report_resp.data will contains the report. The report
+contain the format described in the SEV-SNP specification. See the SEV-SNP
+specification for further details.
+
+2.2 SNP_GET_DERIVED_KEY
+-----------------------
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in): struct snp_derived_key_req
+:Returns (out): struct snp_derived_key_resp on success, -negative on error
+
+The SNP_GET_DERIVED_KEY ioctl can be used to get a key derive from a root key.
+The derived key can be used by the guest for any purpose, such as sealing keys
+or communicating with external entities.
+
+The ioctl uses the SNP_GUEST_REQUEST (MSG_KEY_REQ) command provided by the
+SEV-SNP firmware to derive the key. See SEV-SNP specification for further details
+on the various fields passed in the key derivation request.
+
+On success, the snp_derived_key_resp.data contains the derived key value. See
+the SEV-SNP specification for further details.
+
+
+2.3 SNP_GET_EXT_REPORT
+----------------------
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in/out): struct snp_ext_report_req
+:Returns (out): struct snp_report_resp on success, -negative on error
+
+The SNP_GET_EXT_REPORT ioctl is similar to the SNP_GET_REPORT. The difference is
+related to the additional certificate data that is returned with the report.
+The certificate data returned is being provided by the hypervisor through the
+SNP_SET_EXT_CONFIG.
+
+The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command provided by the SEV-SNP
+firmware to get the attestation report.
+
+On success, the snp_ext_report_resp.data will contain the attestation report
+and snp_ext_report_req.certs_address will contain the certificate blob. If the
+length of the blob is smaller than expected then snp_ext_report_req.certs_len will
+be updated with the expected value.
+
+See GHCB specification for further detail on how to parse the certificate blob.
+
+3. SEV-SNP CPUID Enforcement
+============================
+
+SEV-SNP guests can access a special page that contains a table of CPUID values
+that have been validated by the PSP as part of the SNP_LAUNCH_UPDATE firmware
+command. It provides the following assurances regarding the validity of CPUID
+values:
+
+ - Its address is obtained via bootloader/firmware (via CC blob), and those
+ binaries will be measured as part of the SEV-SNP attestation report.
+ - Its initial state will be encrypted/pvalidated, so attempts to modify
+ it during run-time will result in garbage being written, or #VC exceptions
+ being generated due to changes in validation state if the hypervisor tries
+ to swap the backing page.
+ - Attempts to bypass PSP checks by the hypervisor by using a normal page, or
+ a non-CPUID encrypted page will change the measurement provided by the
+ SEV-SNP attestation report.
+ - The CPUID page contents are *not* measured, but attempts to modify the
+ expected contents of a CPUID page as part of guest initialization will be
+ gated by the PSP CPUID enforcement policy checks performed on the page
+ during SNP_LAUNCH_UPDATE, and noticeable later if the guest owner
+ implements their own checks of the CPUID values.
+
+It is important to note that this last assurance is only useful if the kernel
+has taken care to make use of the SEV-SNP CPUID throughout all stages of boot.
+Otherwise, guest owner attestation provides no assurance that the kernel wasn't
+fed incorrect values at some point during boot.
+
+
+Reference
+---------
+
+SEV-SNP and GHCB specification: developer.amd.com/sev
+
+The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
diff --git a/Documentation/virt/coco/tdx-guest.rst b/Documentation/virt/coco/tdx-guest.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+TDX Guest API Documentation
+===================================================================
+
+1. General description
+======================
+
+The TDX guest driver exposes IOCTL interfaces via the /dev/tdx-guest misc
+device to allow userspace to get certain TDX guest-specific details.
+
+2. API description
+==================
+
+In this section, for each supported IOCTL, the following information is
+provided along with a generic description.
+
+:Input parameters: Parameters passed to the IOCTL and related details.
+:Output: Details about output data and return value (with details about
+ the non common error values).
+
+2.1 TDX_CMD_GET_REPORT0
+-----------------------
+
+:Input parameters: struct tdx_report_req
+:Output: Upon successful execution, TDREPORT data is copied to
+ tdx_report_req.tdreport and return 0. Return -EINVAL for invalid
+ operands, -EIO on TDCALL failure or standard error number on other
+ common failures.
+
+The TDX_CMD_GET_REPORT0 IOCTL can be used by the attestation software to get
+the TDREPORT0 (a.k.a. TDREPORT subtype 0) from the TDX module using
+TDCALL[TDG.MR.REPORT].
+
+A subtype index is added at the end of this IOCTL CMD to uniquely identify the
+subtype-specific TDREPORT request. Although the subtype option is mentioned in
+the TDX Module v1.0 specification, section titled "TDG.MR.REPORT", it is not
+currently used, and it expects this value to be 0. So to keep the IOCTL
+implementation simple, the subtype option was not included as part of the input
+ABI. However, in the future, if the TDX Module supports more than one subtype,
+a new IOCTL CMD will be created to handle it. To keep the IOCTL naming
+consistent, a subtype index is added as part of the IOCTL CMD.
+
+Reference
+---------
+
+TDX reference material is collected here:
+
+https://www.intel.com/content/www/us/en/developer/articles/technical/intel-trust-domain-extensions.html
+
+The driver is based on TDX module specification v1.0 and TDX GHCI specification v1.0.