linux-kernel - [PATCH v2 00/11] Add Secure TSC support for SNP guests

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Message-ID: <20230326144701.3039598-1-nikunj@amd.com>
Date:   Sun, 26 Mar 2023 20:16:50 +0530
From:   Nikunj A Dadhania <nikunj@....com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <bp@...en8.de>, <thomas.lendacky@....com>,
        <dionnaglaze@...gle.com>, <pgonda@...gle.com>, <seanjc@...gle.com>,
        <pbonzini@...hat.com>, <nikunj@....com>, <michael.roth@....com>,
        <ketanch@...k.ac.in>
Subject: [PATCH v2 00/11] Add Secure TSC support for SNP guests

Secure TSC allows guest to securely use RDTSC/RDTSCP instructions as the
parameters being used cannot be changed by hypervisor once the guest is
launched. More details in the AMD64 APM Vol 2, Section "Secure TSC".

During the boot-up of the secondary cpus, SecureTSC enabled guests need to
query TSC info from Security processor (PSP). This communication channel is
encrypted between the security processor and the guest, hypervisor is just
the conduit to deliver the guest messages to the security processor. Each
message is protected with an AEAD (AES-256 GCM). See "SEV Secure Nested
Paging Firmware ABI Specification" document (currently at
https://www.amd.com/system/files/TechDocs/56860.pdf) section "TSC Info"

Use minimal GCM library to encrypt/decrypt SNP Guest messages to
communicate with the PSP which is available at earlyboot.

SEV-guest driver has the implementation for guest and security coprocessor
communication. As the TSC_INFO needs to be initialized during early boot
before smp cpus are started, move most of the sev-guest driver code as part
to kernel/sev.c and provide well defined APIs to the sev-guest driver to
use the interface to avoid code-duplication.

Patches:
01-05: Preparation and movement of sev-guest driver code
   06: Adds generic guest initialization hook
07-11: SecureTSC enablement patches.

Testing SecureTSC
-----------------

SecureTSC hypervisor patches based on top of SEV-SNP UPM series:
https://github.com/nikunjad/linux/tree/upmv10-snpv8_securetsc

QEMU changes:
https://github.com/nikunjad/qemu/tree/upmv10b-snpv3-wip-securetsc

QEMU commandline SEV-SNP-UPM with SecureTSC:

  qemu-system-x86_64 -cpu EPYC-Milan-v2 \
    -object memory-backend-memfd-private,id=ram1,size=1G,share=true \
    -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,secure-tsc=on \
    -machine q35,confidential-guest-support=sev0,memory-backend=ram1,kvm-type=protected \
    ...

Changelog:
----------
v2:
* Rebased on top of v6.3-rc3 that has Boris's sev-guest cleanup series
  https://lore.kernel.org/r/20230307192449.24732-1-bp@alien8.de/

v1: https://lore.kernel.org/r/20230130120327.977460-1-nikunj@amd.com/

Nikunj A Dadhania (11):
  virt: sev-guest: Use AES GCM crypto library
  virt: sev-guest: Move mutex to SNP guest device structure
  virt: sev-guest: Add snp_guest_req structure
  virt: sev-guest: Add simplified helper to assign vmpck
  x86/sev: Move and reorganize sev guest request api
  x86/mm: Add generic guest initialization hook
  x86/sev: Change TSC MSR behavior for Secure TSC enabled guests
  x86/sev: Add Secure TSC support for SNP guests
  x86/kvmclock: Use Secure TSC as clock if available
  x86/tsc: Mark Secure TSC as reliable clocksource
  x86/sev: Enable Secure TSC for SNP guests

 arch/x86/Kconfig                              |   1 +
 arch/x86/boot/compressed/sev.c                |   2 +-
 arch/x86/coco/core.c                          |   3 +
 .../x86/include/asm}/sev-guest.h              |  46 ++
 arch/x86/include/asm/sev.h                    |  24 +
 arch/x86/include/asm/svm.h                    |   6 +-
 arch/x86/include/asm/x86_init.h               |   2 +
 arch/x86/kernel/kvmclock.c                    |   2 +-
 arch/x86/kernel/sev-shared.c                  |   7 +
 arch/x86/kernel/sev.c                         | 541 +++++++++++++++-
 arch/x86/kernel/tsc.c                         |   2 +-
 arch/x86/kernel/x86_init.c                    |   2 +
 arch/x86/mm/mem_encrypt.c                     |  13 +-
 arch/x86/mm/mem_encrypt_amd.c                 |   6 +
 drivers/virt/coco/sev-guest/Kconfig           |   2 -
 drivers/virt/coco/sev-guest/sev-guest.c       | 592 ++----------------
 include/linux/cc_platform.h                   |   8 +
 17 files changed, 708 insertions(+), 551 deletions(-)
 rename {drivers/virt/coco/sev-guest => arch/x86/include/asm}/sev-guest.h (54%)

base-commit: e8d018dd0257f744ca50a729e3d042cf2ec9da65
-- 
2.34.1