Commit eb39e37d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86_sev_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull AMD SEV-SNP support from Borislav Petkov:
 "The third AMD confidential computing feature called Secure Nested
  Paging.

  Add to confidential guests the necessary memory integrity protection
  against malicious hypervisor-based attacks like data replay, memory
  remapping and others, thus achieving a stronger isolation from the
  hypervisor.

  At the core of the functionality is a new structure called a reverse
  map table (RMP) with which the guest has a say in which pages get
  assigned to it and gets notified when a page which it owns, gets
  accessed/modified under the covers so that the guest can take an
  appropriate action.

  In addition, add support for the whole machinery needed to launch a
  SNP guest, details of which is properly explained in each patch.

  And last but not least, the series refactors and improves parts of the
  previous SEV support so that the new code is accomodated properly and
  not just bolted on"

* tag 'x86_sev_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits)
  x86/entry: Fixup objtool/ibt validation
  x86/sev: Mark the code returning to user space as syscall gap
  x86/sev: Annotate stack change in the #VC handler
  x86/sev: Remove duplicated assignment to variable info
  x86/sev: Fix address space sparse warning
  x86/sev: Get the AP jump table address from secrets page
  x86/sev: Add missing __init annotations to SEV init routines
  virt: sevguest: Rename the sevguest dir and files to sev-guest
  virt: sevguest: Change driver name to reflect generic SEV support
  x86/boot: Put globals that are accessed early into the .data section
  x86/boot: Add an efi.h header for the decompressor
  virt: sevguest: Fix bool function returning negative value
  virt: sevguest: Fix return value check in alloc_shared_pages()
  x86/sev-es: Replace open-coded hlt-loop with sev_es_terminate()
  virt: sevguest: Add documentation for SEV-SNP CPUID Enforcement
  virt: sevguest: Add support to get extended report
  virt: sevguest: Add support to derive key
  virt: Add SEV-SNP guest driver
  x86/sev: Register SEV-SNP guest request platform device
  x86/sev: Provide support for SNP guest request NAEs
  ...
parents 0be3ff0c ce656528

Documentation/admin-guide/kernel-parameters.txt

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@@ -5383,6 +5383,8 @@ 


	serialnumber	[BUGS=X86-32]



	sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst



	shapers=	[NET]

			Maximal number of shapers.

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 fw_err code will be set otherwise the

fw_err will be set to 0x00000000000000ff.



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;



                /* firmware error code on failure (see psp-sev.h) */

                __u64 fw_err;

        };



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.

Documentation/virt/index.rst

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@@ -13,6 +13,7 @@ Linux Virtualization Support 
   guest-halt-polling

   ne_overview

   acrn/index

   coco/sev-guest



.. only:: html and subproject

Documentation/x86/x86_64/boot-options.rst

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@@ -310,3 +310,17 @@ Miscellaneous 
    Do not use GB pages for kernel direct mappings.

  gbpages

    Use GB pages for kernel direct mappings.





AMD SEV (Secure Encrypted Virtualization)

=========================================

Options relating to AMD SEV, specified via the following format:



::



   sev=option1[,option2]



The available options are:



   debug

     Enable debug messages.

Documentation/x86/zero-page.rst

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@@ -19,6 +19,7 @@ Offset/Size Proto Name Meaning 
058/008		ALL	tboot_addr      	Physical address of tboot shared page

060/010		ALL	ist_info		Intel SpeedStep (IST) BIOS support information

						(struct ist_info)

070/008		ALL	acpi_rsdp_addr		Physical address of ACPI RSDP table

080/010		ALL	hd0_info		hd0 disk parameter, OBSOLETE!!

090/010		ALL	hd1_info		hd1 disk parameter, OBSOLETE!!

0A0/010		ALL	sys_desc_table		System description table (struct sys_desc_table),
@@ -27,6 +28,7 @@ Offset/Size Proto Name Meaning 
0C0/004		ALL	ext_ramdisk_image	ramdisk_image high 32bits

0C4/004		ALL	ext_ramdisk_size	ramdisk_size high 32bits

0C8/004		ALL	ext_cmd_line_ptr	cmd_line_ptr high 32bits

13C/004		ALL	cc_blob_address		Physical address of Confidential Computing blob

140/080		ALL	edid_info		Video mode setup (struct edid_info)

1C0/020		ALL	efi_info		EFI 32 information (struct efi_info)

1E0/004		ALL	alt_mem_k		Alternative mem check, in KB