From: Tom Lendacky <thomas.lendacky@amd.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Brijesh Singh <brijesh.singh@amd.com>
Cc: 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: Fri, 11 Jun 2021 08:16:58 -0500 [thread overview]
Message-ID: <8a598020-7d89-b399-efb9-735b2a6da8a9@amd.com> (raw)
In-Reply-To: <YMEVedGOrYgI1Klc@work-vm>
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.
>
>> + 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.
I'll let Brijesh address the other questions.
Thanks,
Tom
next prev parent reply other threads:[~2021-06-11 13:17 UTC|newest]
Thread overview: 100+ 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
2021-06-23 4:30 ` Michael Roth
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 [this message]
2021-06-14 17:15 ` Dr. David Alan Gilbert
2021-06-14 18:24 ` Brijesh Singh
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
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