From: Brijesh Singh <brijesh.singh@amd.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Cc: brijesh.singh@amd.com, x86@kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
linux-coco@lists.linux.dev, linux-mm@kvack.org,
linux-crypto@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
tony.luck@intel.com, npmccallum@redhat.com
Subject: Re: [PATCH Part1 RFC v3 21/22] x86/sev: Register SNP guest request platform device
Date: Mon, 14 Jun 2021 13:24:25 -0500 [thread overview]
Message-ID: <ae1f211a-3606-1624-fa8a-8df404e87e9e@amd.com> (raw)
In-Reply-To: <YMeOnO4PBnvxEQEv@work-vm>
On 6/14/21 12:15 PM, Dr. David Alan Gilbert wrote:
> * Tom Lendacky (thomas.lendacky@amd.com) wrote:
>> On 6/9/21 2:24 PM, Dr. David Alan Gilbert wrote:
>>> * Brijesh Singh (brijesh.singh@amd.com) wrote:
>>>> Version 2 of GHCB specification provides NAEs that can be used by the SNP
>>>> guest to communicate with the PSP without risk from a malicious hypervisor
>>>> who wishes to read, alter, drop or replay the messages sent.
>>>>
>>>> The hypervisor uses the SNP_GUEST_REQUEST command interface provided by
>>>> the SEV-SNP firmware to forward the guest messages to the PSP.
>>>>
>>>> In order to communicate with the PSP, the guest need to locate the secrets
>>>> page inserted by the hypervisor during the SEV-SNP guest launch. The
>>>> secrets page contains the communication keys used to send and receive the
>>>> encrypted messages between the guest and the PSP.
>>>>
>>>> The secrets page is located either through the setup_data cc_blob_address
>>>> or EFI configuration table.
>>>>
>>>> Create a platform device that the SNP guest driver can bind to get the
>>>> platform resources. The SNP guest driver can provide userspace interface
>>>> to get the attestation report, key derivation etc.
>>>>
>>>> The helper snp_issue_guest_request() will be used by the drivers to
>>>> send the guest message request to the hypervisor. The guest message header
>>>> contains a message count. The message count is used in the IV. The
>>>> firmware increments the message count by 1, and expects that next message
>>>> will be using the incremented count.
>>>>
>>>> The helper snp_msg_seqno() will be used by driver to get and message
>>>> sequence counter, and it will be automatically incremented by the
>>>> snp_issue_guest_request(). The incremented value is be saved in the
>>>> secrets page so that the kexec'ed kernel knows from where to begin.
>>>>
>>>> See SEV-SNP and GHCB spec for more details.
>>>>
>>>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>>>> ---
>>>> arch/x86/include/asm/sev.h | 12 +++
>>>> arch/x86/include/uapi/asm/svm.h | 2 +
>>>> arch/x86/kernel/sev.c | 176 ++++++++++++++++++++++++++++++++
>>>> arch/x86/platform/efi/efi.c | 2 +
>>>> include/linux/efi.h | 1 +
>>>> include/linux/sev-guest.h | 76 ++++++++++++++
>>>> 6 files changed, 269 insertions(+)
>>>> create mode 100644 include/linux/sev-guest.h
>>>>
>>>> +u64 snp_msg_seqno(void)
>>>> +{
>>>> + struct snp_secrets_page_layout *layout;
>>>> + u64 count;
>>>> +
>>>> + layout = snp_map_secrets_page();
>>>> + if (layout == NULL)
>>>> + return 0;
>>>> +
>>>> + /* Read the current message sequence counter from secrets pages */
>>>> + count = readl(&layout->os_area.msg_seqno_0);
>>> Why is this seqno_0 - is that because it's the count of talking to the
>>> PSP?
>> Yes, the sequence number is an ever increasing value that is used in
>> communicating with the PSP. The PSP maintains the next expected sequence
>> number and will reject messages which have a sequence number that is not
>> in sync with the PSP. The 0 refers to the VMPL level. Each VMPL level has
>> its own sequence number.
> Can you just clarify; is that the VMPL of the caller or the destination?
> What I'm partially asking here is whether it matters which VMPL the
> kernel is running at (which I'm assuming could well be non-0)
The caller's VMPL number. Each VMPL have different communicate keys,
please see the secrets page layout as described in the SEV-SNP firmware
spec 8.14.2.5[1].
As indicated in the cover letter, the guest and hypervisor patches are
targeted to for VMPL0 so we are using sequence number and key from the
vmpl0 only.
[1] https://www.amd.com/system/files/TechDocs/56860.pdf
>
>>>> + iounmap(layout);
>>>> +
>>>> + /*
>>>> + * The message sequence counter for the SNP guest request is a 64-bit value
>>>> + * but the version 2 of GHCB specification defines the 32-bit storage for the
>>>> + * it.
>>>> + */
>>>> + if ((count + 1) >= INT_MAX)
>>>> + return 0;
>>> Is that UINT_MAX?
>>>
>>>> +
>>>> + return count + 1;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(snp_msg_seqno);
>>>> +
>>>> +static void snp_gen_msg_seqno(void)
>>>> +{
>>>> + struct snp_secrets_page_layout *layout;
>>>> + u64 count;
>>>> +
>>>> + layout = snp_map_secrets_page();
>>>> + if (layout == NULL)
>>>> + return;
>>>> +
>>>> + /* Increment the sequence counter by 2 and save in secrets page. */
>>>> + count = readl(&layout->os_area.msg_seqno_0);
>>>> + count += 2;
>>> Why 2 not 1 ?
>> The return message by the PSP also increments the sequence number, hence
>> the increment by 2 instead of 1 for the next message to be submitted.
> OK
>
> Dave
>
>> I'll let Brijesh address the other questions.
>>
>> Thanks,
>> Tom
>>
next prev parent reply other threads:[~2021-06-14 18:24 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-02 14:03 [PATCH Part1 RFC v3 00/22] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2021-06-02 14:03 ` [PATCH Part1 RFC v3 01/22] x86/sev: shorten GHCB terminate macro names Brijesh Singh
2021-06-08 15:54 ` Venu Busireddy
2021-06-02 14:03 ` [PATCH Part1 RFC v3 02/22] x86/sev: Define the Linux specific guest termination reasons Brijesh Singh
2021-06-08 15:59 ` Venu Busireddy
2021-06-08 16:51 ` Brijesh Singh
2021-06-02 14:03 ` [PATCH Part1 RFC v3 03/22] x86/sev: Save the negotiated GHCB version Brijesh Singh
2021-06-03 19:57 ` Borislav Petkov
2021-06-08 17:35 ` Venu Busireddy
2021-06-02 14:03 ` [PATCH Part1 RFC v3 04/22] x86/mm: Add sev_feature_enabled() helper Brijesh Singh
2021-06-05 10:50 ` Borislav Petkov
2021-06-02 14:03 ` [PATCH Part1 RFC v3 05/22] x86/sev: Add support for hypervisor feature VMGEXIT Brijesh Singh
2021-06-07 14:19 ` Borislav Petkov
2021-06-07 14:58 ` Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 06/22] x86/sev: check SEV-SNP features support Brijesh Singh
2021-06-07 14:54 ` Borislav Petkov
2021-06-07 16:01 ` Brijesh Singh
2021-06-17 18:46 ` Brijesh Singh
2021-06-18 5:46 ` Borislav Petkov
2021-06-02 14:04 ` [PATCH Part1 RFC v3 07/22] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2021-06-07 15:35 ` Borislav Petkov
2021-06-02 14:04 ` [PATCH Part1 RFC v3 08/22] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2021-06-08 11:12 ` Borislav Petkov
2021-06-08 15:58 ` Brijesh Singh
2021-06-16 10:21 ` Borislav Petkov
2021-06-02 14:04 ` [PATCH Part1 RFC v3 09/22] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2021-06-09 17:47 ` Borislav Petkov
2021-06-14 12:28 ` Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 10/22] x86/sev: " Brijesh Singh
2021-06-10 5:49 ` Borislav Petkov
2021-06-14 12:29 ` Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 11/22] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2021-06-10 15:50 ` Borislav Petkov
2021-06-14 12:45 ` Brijesh Singh
2021-06-14 19:03 ` Borislav Petkov
2021-06-14 21:01 ` Brijesh Singh
2021-06-16 10:07 ` Borislav Petkov
2021-06-16 11:00 ` Brijesh Singh
2021-06-16 12:03 ` Borislav Petkov
2021-06-16 12:49 ` Brijesh Singh
2021-06-16 13:02 ` Borislav Petkov
2021-06-16 13:10 ` Brijesh Singh
2021-06-16 14:36 ` Brijesh Singh
2021-06-16 14:37 ` Brijesh Singh
2021-06-16 13:06 ` Dr. David Alan Gilbert
2021-06-02 14:04 ` [PATCH Part1 RFC v3 12/22] x86/kernel: Make the bss.decrypted section shared in RMP table Brijesh Singh
2021-06-10 16:06 ` Borislav Petkov
2021-06-02 14:04 ` [PATCH Part1 RFC v3 13/22] x86/kernel: Validate rom memory before accessing when SEV-SNP is active Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 14/22] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2021-06-11 9:44 ` Borislav Petkov
2021-06-14 13:05 ` Brijesh Singh
2021-06-14 19:27 ` Borislav Petkov
2021-06-02 14:04 ` [PATCH Part1 RFC v3 15/22] KVM: SVM: define new SEV_FEATURES field in the VMCB Save State Area Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 16/22] KVM: SVM: Create a separate mapping for the SEV-ES save area Brijesh Singh
2021-06-14 10:58 ` Borislav Petkov
2021-06-14 19:34 ` Tom Lendacky
2021-06-14 19:50 ` Borislav Petkov
2021-06-02 14:04 ` [PATCH Part1 RFC v3 17/22] KVM: SVM: Create a separate mapping for the GHCB " Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 18/22] KVM: SVM: Update the SEV-ES save area mapping Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 19/22] x86/sev-snp: SEV-SNP AP creation support Brijesh Singh
2021-06-16 13:07 ` Borislav Petkov
2021-06-16 16:13 ` Tom Lendacky
2021-06-02 14:04 ` [PATCH Part1 RFC v3 20/22] x86/boot: Add Confidential Computing address to setup_header Brijesh Singh
2021-06-18 6:08 ` Borislav Petkov
2021-06-18 13:57 ` Brijesh Singh
2021-06-18 15:05 ` Borislav Petkov
[not found] ` <162442264313.98837.16983159316116149849@amd.com>
2021-06-23 10:22 ` Borislav Petkov
2021-06-24 3:19 ` Michael Roth
2021-06-24 7:27 ` Borislav Petkov
2021-06-24 12:26 ` Michael Roth
2021-06-24 12:34 ` Michael Roth
2021-06-24 12:54 ` Borislav Petkov
2021-06-24 14:11 ` Michael Roth
2021-06-25 14:48 ` Borislav Petkov
2021-06-25 15:24 ` Brijesh Singh
2021-06-25 17:01 ` Borislav Petkov
2021-06-25 18:14 ` Michael Roth
2021-06-28 13:43 ` Borislav Petkov
2021-06-24 13:09 ` Kuppuswamy, Sathyanarayanan
2021-06-02 14:04 ` [PATCH Part1 RFC v3 21/22] x86/sev: Register SNP guest request platform device Brijesh Singh
2021-06-04 11:28 ` Sergio Lopez
2021-06-09 19:24 ` Dr. David Alan Gilbert
2021-06-11 13:16 ` Tom Lendacky
2021-06-14 17:15 ` Dr. David Alan Gilbert
2021-06-14 18:24 ` Brijesh Singh [this message]
2021-06-14 13:20 ` Brijesh Singh
2021-06-14 17:23 ` Dr. David Alan Gilbert
2021-06-14 20:50 ` Brijesh Singh
2021-06-18 9:46 ` Borislav Petkov
2021-06-18 13:59 ` Brijesh Singh
2021-06-02 14:04 ` [PATCH Part1 RFC v3 22/22] virt: Add SEV-SNP guest driver Brijesh Singh
2021-06-30 13:35 ` Borislav Petkov
2021-06-30 16:26 ` Brijesh Singh
2021-07-01 18:03 ` Borislav Petkov
2021-07-01 21:32 ` Brijesh Singh
2021-07-03 16:19 ` Borislav Petkov
2021-07-05 10:39 ` Brijesh Singh
2021-06-07 19:15 ` [PATCH Part1 RFC v3 00/22] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Venu Busireddy
2021-06-07 19:17 ` Borislav Petkov
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=ae1f211a-3606-1624-fa8a-8df404e87e9e@amd.com \
--to=brijesh.singh@amd.com \
--cc=ardb@kernel.org \
--cc=dave.hansen@linux.intel.com \
--cc=dgilbert@redhat.com \
--cc=hpa@zytor.com \
--cc=jmattson@google.com \
--cc=jroedel@suse.de \
--cc=kvm@vger.kernel.org \
--cc=linux-coco@lists.linux.dev \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-efi@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=npmccallum@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=pgonda@google.com \
--cc=platform-driver-x86@vger.kernel.org \
--cc=rientjes@google.com \
--cc=seanjc@google.com \
--cc=slp@redhat.com \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=tony.luck@intel.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.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;
as well as URLs for NNTP newsgroup(s).