From: "Nikunj A. Dadhania" <nikunj@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
kvm@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de,
dave.hansen@linux.intel.com, seanjc@google.com,
pbonzini@redhat.com, thomas.lendacky@amd.com,
michael.roth@amd.com, stable@kernel.org
Subject: Re: [PATCH v3] x86/sev: Add SEV-SNP guest feature negotiation support
Date: Wed, 4 Jan 2023 09:56:21 +0530 [thread overview]
Message-ID: <46ec426b-e6bb-5286-77c2-1c4cf1fdda93@amd.com> (raw)
In-Reply-To: <Y7QwXcAUmS3VZcbH@zn.tnic>
On 03/01/23 19:10, Borislav Petkov wrote:
> On Mon, Jan 02, 2023 at 02:08:10PM +0530, Nikunj A Dadhania wrote:
>> The hypervisor can enable various new features (SEV_FEATURES[1:63])
>> and start the SNP guest. Some of these features need guest side
>> implementation. If any of these features are enabled without guest
>> side implementation, the behavior of the SNP guest will be undefined.
>> The SNP guest boot may fail in a non-obvious way making it difficult
>> to debug.
>>
>> Instead of allowing the guest to continue and have it fail randomly
>> later, detect this early and fail gracefully.
>>
>> SEV_STATUS MSR indicates features which hypervisor has enabled. While
> ^
> the
Sure.
>
>> booting, SNP guests should ascertain that all the enabled features
>> have guest side implementation. In case any feature is not implemented
>> in the guest, the guest terminates booting with SNP feature
>> unsupported exit code.
>>
>> More details in AMD64 APM[1] Vol 2: 15.34.10 SEV_STATUS MSR
>>
>> [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.amd.com%2Fsystem%2Ffiles%2FTechDocs%2F40332_4.05.pdf&data=05%7C01%7Cnikunj.dadhania%40amd.com%7C6575db7c0d8f4f136d1f08daed902274%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638083500715058552%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=weTrXWfPxDBdu9OsFZ4FxlvlgbhhG%2F985%2Bii%2BM8vh6I%3D&reserved=0
>>
>> Fixes: cbd3d4f7c4e5 ("x86/sev: Check SEV-SNP features support")
>> CC: Borislav Petkov <bp@alien8.de>
>> CC: Michael Roth <michael.roth@amd.com>
>> CC: Tom Lendacky <thomas.lendacky@amd.com>
>> CC: <stable@kernel.org>
>> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
>
> ...
>
>> diff --git a/Documentation/x86/amd-memory-encryption.rst b/Documentation/x86/amd-memory-encryption.rst
>> index a1940ebe7be5..b8b6b87be995 100644
>> --- a/Documentation/x86/amd-memory-encryption.rst
>> +++ b/Documentation/x86/amd-memory-encryption.rst
>> @@ -95,3 +95,38 @@ by supplying mem_encrypt=on on the kernel command line. However, if BIOS does
>> not enable SME, then Linux will not be able to activate memory encryption, even
>> if configured to do so by default or the mem_encrypt=on command line parameter
>> is specified.
>> +
>> +Secure Nested Paging (SNP):
>
> No ":"
>
Done
>> +===========================
>
> <---- newline here.
Done
>
>> +SEV-SNP introduces new features (SEV_FEATURES[1:63]) which can be enabled
>> +by the hypervisor for security enhancements. Some of these features need
>> +guest side implementation to function correctly. The below table lists the
>> +expected guest behavior with various possible scenarios of guest/hypervisor
>> +SNP feature support.
>> +
>> ++---------------+---------------+---------------+---------------+
>> +|Feature Enabled| Guest needs | Guest has | Guest boot |
>> +| by HV |implementation |implementation | behavior |
>> ++---------------+---------------+---------------+---------------+
>> +| No | No | No | Boot |
>> +| | | | |
>> ++---------------+---------------+---------------+---------------+
>> +| No | Yes | No | Boot |
>> +| | | | |
>> ++---------------+---------------+---------------+---------------+
>> +| No | Yes | Yes | Boot |
>> +| | | | |
>> ++---------------+---------------+---------------+---------------+
>> +| Yes | No | No | Boot with |
>> +| | | |feature enabled|
>> ++---------------+---------------+---------------+---------------+
>> +| Yes | Yes | No | Graceful Boot |
>> +| | | | Failure |
>> ++---------------+---------------+---------------+---------------+
>> +| Yes | Yes | Yes | Boot with |
>> +| | | |feature enabled|
>> ++---------------+---------------+---------------+---------------+
>
> sphinx is not happy about that table for some reason. I always find the error
> messages cryptic though:
sphinx uses spaces before multi-line text as block quote. Also, found that after the table header it needs line with "=" and not "-".
> Documentation/x86/amd-memory-encryption.rst:110: WARNING: Block quote ends without a blank line; unexpected unindent.
> Documentation/x86/amd-memory-encryption.rst:110: WARNING: Block quote ends without a blank line; unexpected unindent.
> Documentation/x86/amd-memory-encryption.rst:122: WARNING: Block quote ends without a blank line; unexpected unindent.
> Documentation/x86/amd-memory-encryption.rst:128: WARNING: Block quote ends without a blank line; unexpected unindent.
>
> You can repro by doing "make htmldocs".
Fixed,
+-----------------+---------------+---------------+------------------+
| Feature Enabled | Guest needs | Guest has | Guest boot |
| by the HV | implementation| implementation| behaviour |
+=================+===============+===============+==================+
| No | No | No | Boot |
| | | | |
+-----------------+---------------+---------------+------------------+
| No | Yes | No | Boot |
| | | | |
+-----------------+---------------+---------------+------------------+
| No | Yes | Yes | Boot |
| | | | |
+-----------------+---------------+---------------+------------------+
| Yes | No | No | Boot with |
| | | | feature enabled |
+-----------------+---------------+---------------+------------------+
| Yes | Yes | No | Graceful boot |
| | | | failure |
+-----------------+---------------+---------------+------------------+
| Yes | Yes | Yes | Boot with |
| | | | feature enabled |
+-----------------+---------------+---------------+------------------+
Regards
Nikunj
prev parent reply other threads:[~2023-01-04 4:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-02 8:38 [PATCH v3] x86/sev: Add SEV-SNP guest feature negotiation support Nikunj A Dadhania
2023-01-02 11:23 ` David Rientjes
2023-01-02 15:20 ` Nikunj A. Dadhania
2023-01-02 19:42 ` Borislav Petkov
2023-01-03 3:25 ` Nikunj A. Dadhania
2023-01-02 20:02 ` Borislav Petkov
2023-01-03 3:37 ` Nikunj A. Dadhania
2023-01-03 11:29 ` Borislav Petkov
2023-01-03 23:25 ` David Rientjes
2023-01-03 13:40 ` Borislav Petkov
2023-01-04 4:26 ` Nikunj A. Dadhania [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=46ec426b-e6bb-5286-77c2-1c4cf1fdda93@amd.com \
--to=nikunj@amd.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=michael.roth@amd.com \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=stable@kernel.org \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox