From: Tom Lendacky <thomas.lendacky@amd.com>
To: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Dan Williams <dan.j.williams@intel.com>,
Michael Roth <michael.roth@amd.com>,
Ashish Kalra <ashish.kalra@amd.com>
Subject: Re: [PATCH v2 11/14] x86/sev: Extend the config-fs attestation support for an SVSM
Date: Tue, 12 Mar 2024 08:29:34 -0500 [thread overview]
Message-ID: <02ac2f5d-6e56-46ef-b5fd-7c1503600f1d@amd.com> (raw)
In-Reply-To: <fa7cee6f-954b-4acf-a438-17ae3d1e781a@linux.intel.com>
On 3/12/24 00:57, Kuppuswamy Sathyanarayanan wrote:
>
> On 3/11/24 9:16 AM, Tom Lendacky wrote:
>> On 3/10/24 00:06, Kuppuswamy, Sathyanarayanan wrote:
>>>
>>> On 3/8/24 10:35 AM, Tom Lendacky wrote:
>>>> When an SVSM is present, the guest can also request attestation reports
>>>> from the SVSM. These SVSM attestation reports can be used to attest the
>>>> SVSM and any services running within the SVSM.
>>>>
>>>> Extend the config-fs attestation support to allow for an SVSM attestation
>>>> report. This involves creating four (4) new config-fs attributes:
>>>>
>>>> - 'svsm' (input)
>>>> This attribute is used to determine whether the attestation request
>>>> should be sent to the SVSM or to the SEV firmware.
>>>>
>>>> - 'service_guid' (input)
>>>> Used for requesting the attestation of a single service within the
>>>> SVSM. A null GUID implies that the SVSM_ATTEST_SERVICES call should
>>>> be used to request the attestation report. A non-null GUID implies
>>>> that the SVSM_ATTEST_SINGLE_SERVICE call should be used.
>>>>
>>>> - 'service_manifest_version' (input)
>>>> Used with the SVSM_ATTEST_SINGLE_SERVICE call, the service version
>>>> represents a specific service manifest version be used for the
>>>> attestation report.
>>>>
>>>> - 'manifestblob' (output)
>>>> Used to return the service manifest associated with the attestation
>>>> report.
>>>>
>>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>>> ---
>>>> Documentation/ABI/testing/configfs-tsm | 59 ++++++++++
>>>> arch/x86/include/asm/sev.h | 31 ++++-
>>>> arch/x86/kernel/sev.c | 50 ++++++++
>>>> drivers/virt/coco/sev-guest/sev-guest.c | 147 ++++++++++++++++++++++++
>>>> drivers/virt/coco/tsm.c | 95 ++++++++++++++-
>>>> include/linux/tsm.h | 11 ++
>>>> 6 files changed, 390 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/Documentation/ABI/testing/configfs-tsm b/Documentation/ABI/testing/configfs-tsm
>>>> index dd24202b5ba5..a4663610bf7c 100644
>>>> --- a/Documentation/ABI/testing/configfs-tsm
>>>> +++ b/Documentation/ABI/testing/configfs-tsm
>>
>>>> +
>>>> +What: /sys/kernel/config/tsm/report/$name/service_guid
>>>> +Date: January, 2024
>>>> +KernelVersion: v6.9
>>>> +Contact: linux-coco@lists.linux.dev
>>>> +Description:
>>>> + (WO) Attribute is visible if a TSM implementation provider
>>>> + supports the concept of attestation reports for TVMs running
>>>> + under an SVSM, like SEV-SNP. Specifying a empty or null GUID
>>>> + (00000000-0000-0000-0000-000000) requests all active services
>>>> + within the SVSM be part of the attestation report. Specifying
>>>> + a non-null GUID requests an attestation report of just the
>>>> + specified service using the manifest form specified by the
>>>> + service_manifest_version attribute.
>>>> + Secure VM Service Module for SEV-SNP Guests v1.00 Section 7.
>>>> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
>>>> +
>>>
>>> I think it will be useful to the user if there is a attribute to list the service GUIDs
>>> supported. It can help prevent user using incorrect or unsupported GUIDs.
>>
>> A list of supported GUIDs can be obtained from the manifest of a all-services attestation request.
>
> So they have to make a request twice? Once with a NULL GUID to get the
> manifest with all service list, and another to make service-specific request?
> There should be a fixed list of service GUIDs, right? Why not list them by
> default?
It's not a fixed list. It may appear that way today, but as other services
are added, then it is impossible for a kernel to know what services are
present in the SVSM without querying it.
>
>>
>>
>>>
>>>> + if (guid_len == UUID_STRING_LEN) {
>>>> + rc = guid_parse(buf, &report->desc.service_guid);
>>>> + if (rc)
>>>> + return rc;
>>>> + } else {
>>>> + report->desc.service_guid = guid_null;
>>>
>>> I think the default value will be guid_null right, why reset it to NULL for every failed attempt?
>>
>> Default, yes. But what if it is written once, then a second time with an invalid GUID. Should the previously written GUID still be used?
>>
>
> If the user write fails, why update the state? IMO, we can leave it at the old value. But, lets see what others think.
Sounds good.
Thanks,
Tom
>
>> Thanks,
>> Tom
>>
>>>
next prev parent reply other threads:[~2024-03-12 13:29 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-08 18:35 [PATCH v2 00/14] Provide SEV-SNP support for running under an SVSM Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 01/14] x86/sev: Rename snp_init() in the boot/compressed/sev.c file Tom Lendacky
2024-03-10 21:25 ` Borislav Petkov
2024-03-11 16:16 ` Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 02/14] x86/sev: Make the VMPL0 checking function more generic Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 03/14] x86/sev: Check for the presence of an SVSM in the SNP Secrets page Tom Lendacky
2024-03-09 0:33 ` Dionna Amalie Glaze
2024-03-11 14:50 ` Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 04/14] x86/sev: Use kernel provided SVSM Calling Areas Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 05/14] x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0 Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 06/14] x86/sev: Use the SVSM to create a vCPU when not in VMPL0 Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 07/14] x86/sev: Provide SVSM discovery support Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 08/14] x86/sev: Provide guest VMPL level to userspace Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 09/14] virt: sev-guest: Choose the VMPCK key based on executing VMPL Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 11/14] x86/sev: Extend the config-fs attestation support for an SVSM Tom Lendacky
2024-03-10 6:06 ` Kuppuswamy, Sathyanarayanan
2024-03-11 16:16 ` Tom Lendacky
2024-03-12 5:57 ` Kuppuswamy Sathyanarayanan
2024-03-12 13:29 ` Tom Lendacky [this message]
2024-03-08 18:35 ` [PATCH v2 12/14] fs/configfs: Add a callback to determine attribute visibility Tom Lendacky
2024-03-11 19:58 ` Tom Lendacky
2024-03-13 21:37 ` Joel Becker
2024-03-14 14:23 ` Tom Lendacky
2024-03-21 2:40 ` Dan Williams
2024-03-08 18:35 ` [PATCH v2 13/14] x86/sev: Hide SVSM attestation entries if not running under an SVSM Tom Lendacky
2024-03-23 17:24 ` Kuppuswamy, Sathyanarayanan
2024-03-25 14:05 ` Tom Lendacky
2024-03-26 1:10 ` Kuppuswamy Sathyanarayanan
2024-03-08 18:35 ` [PATCH v2 14/14] x86/sev: Allow non-VMPL0 execution when an SVSM is present Tom Lendacky
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