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The sevguest driver was a first mover in the confidential computing
space. As a first mover that afforded some leeway to build the driver
without concern for common infrastructure.
Now that sevguest is no longer a singleton [1] the common operation of
building and transmitting attestation report blobs can / should be made
common. In this model the so called "TSM-provider" implementations can
share a common envelope ABI even if the contents of that envelope remain
vendor-specific. When / if the industry agrees on an attestation record
format, that definition can also fit in the same ABI. In the meantime
the kernel's maintenance burden is reduced and collaboration on the
commons is increased.
Convert sevguest to use CONFIG_TSM_REPORTS to retrieve the data that
the SNP_GET_EXT_REPORT ioctl produces. An example flow follows for
retrieving the report blob via the TSM interface utility,
assuming no nonce and VMPL==2:
report=/sys/kernel/config/tsm/report/report0
mkdir $report
echo 2 > $report/privlevel
dd if=/dev/urandom bs=64 count=1 > $report/inblob
hexdump -C $report/outblob # SNP report
hexdump -C $report/auxblob # cert_table
rmdir $report
Given that the platform implementation is free to return empty
certificate data if none is available it lets configfs-tsm be simplified
as it only needs to worry about wrapping SNP_GET_EXT_REPORT, and leave
SNP_GET_REPORT alone.
The old ioctls can be lazily deprecated, the main motivation of this
effort is to stop the proliferation of new ioctls, and to increase
cross-vendor collaboration.
Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1]
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Dionna Glaze <dionnaglaze@google.com>
Cc: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Tested-by: Alexey Kardashevskiy <aik@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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The GHCB specification declares that the firmware error value for
a guest request will be stored in the lower 32 bits of EXIT_INFO_2. The
upper 32 bits are for the VMM's own error code. The fw_err argument to
snp_guest_issue_request() is thus a misnomer, and callers will need
access to all 64 bits.
The type of unsigned long also causes problems, since sw_exit_info2 is
u64 (unsigned long long) vs the argument's unsigned long*. Change this
type for issuing the guest request. Pass the ioctl command struct's error
field directly instead of in a local variable, since an incomplete guest
request may not set the error code, and uninitialized stack memory would
be written back to user space.
The firmware might not even be called, so bookend the call with the no
firmware call error and clear the error.
Since the "fw_err" field is really exitinfo2 split into the upper bits'
vmm error code and lower bits' firmware error code, convert the 64 bit
value to a union.
[ bp:
- Massage commit message
- adjust code
- Fix a build issue as
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202303070609.vX6wp2Af-lkp@intel.com
- print exitinfo2 in hex
Tom:
- Correct -EIO exit case. ]
Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230214164638.1189804-5-dionnaglaze@google.com
Link: https://lore.kernel.org/r/20230307192449.24732-12-bp@alien8.de
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Version 2 of GHCB specification defines Non-Automatic-Exit (NAE) to get
extended guest report which is similar to the SNP_GET_REPORT ioctl. The
main difference is related to the additional data that will be returned.
That additional data returned is a certificate blob that can be used by
the SNP guest user. The certificate blob layout is defined in the GHCB
specification. The driver simply treats the blob as a opaque data and
copies it to userspace.
[ bp: Massage commit message, cast 1st arg of access_ok() ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-46-brijesh.singh@amd.com
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The SNP_GET_DERIVED_KEY ioctl interface can be used by the SNP guest to
ask the firmware to provide a key derived from a root key. The derived
key may be used by the guest for any purposes it chooses, such as a
sealing key or communicating with the external entities.
See SEV-SNP firmware spec for more information.
[ bp: No need to memset "req" - it will get overwritten. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-45-brijesh.singh@amd.com
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The SEV-SNP specification provides the guest a mechanism to communicate
with the PSP without risk from a malicious hypervisor who wishes to
read, alter, drop or replay the messages sent. The driver uses
snp_issue_guest_request() to issue GHCB SNP_GUEST_REQUEST or
SNP_EXT_GUEST_REQUEST NAE events to submit the request to PSP.
The PSP requires that all communication should be encrypted using key
specified through a struct snp_guest_platform_data descriptor.
Userspace can use SNP_GET_REPORT ioctl() to query the guest attestation
report.
See SEV-SNP spec section Guest Messages for more details.
[ bp: Remove the "what" from the commit message, massage. ]
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-44-brijesh.singh@amd.com
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