linux-kernel - Re: [PATCH v3 00/14] Add Secure TSC support for SNP guests

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Date:   Tue, 1 Aug 2023 10:17:03 +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
Subject: Re: [PATCH v3 00/14] Add Secure TSC support for SNP guests

On 7/22/2023 4:48 PM, Nikunj A Dadhania wrote:
> Secure TSC allows guests 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 AMD Security Processor. This communication channel is encrypted
> between the AMD Security Processor and the guest, the hypervisor is just the
> conduit to deliver the guest messages to the AMD 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 a minimal GCM library to encrypt/decrypt SNP Guest messages to communicate
> with the AMD Security Processor which is available at early boot.
> 
> SEV-guest driver has the implementation for guest and AMD Security Processor
> 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 to kernel/sev.c and
> provide well defined APIs to the sev-guest driver to use the interface to avoid
> code-duplication.
> 
> Patches:
> 01-07: Preparation and movement of sev-guest driver code
> 08-14: SecureTSC enablement patches.

A gentle reminder.

Thanks
Nikunj

> 
> Testing SecureTSC
> -----------------
> 
> SecureTSC hypervisor patches based on top of SEV-SNP UPM series:
> https://github.com/nikunjad/linux/tree/snp-host-latest-securetsc
> 
> QEMU changes:
> https://github.com/nikunjad/qemu/tree/snp_securetsc
> 
> QEMU commandline SEV-SNP-UPM with SecureTSC:
> 
>   qemu-system-x86_64 -cpu EPYC-Milan-v2,+secure-tsc \
>     -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:
> ----------
> v3:
> * Updated commit messages
> * Made snp_setup_psp_messaging() generic that is accessed by both the
>   kernel and the driver
> * Moved most of the context information to sev.c, sev-guest driver
>   does not need to know the secrets page layout anymore
> * Add CC_ATTR_GUEST_SECURE_TSC early in the series therefore it can be 
>   used in later patches.
> * Removed data_gpa and data_npages from struct snp_req_data, as certs_data 
>   and its size is passed to handle_guest_request_ext()
> * Make vmpck_id as unsigned int
> * Dropped unnecessary usage of memzero_explicit()
> * Cache secrets_pa instead of remapping the cc_blob always
> * Rebase on top of v6.4 kernel
> 
> 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 (14):
>   virt: sev-guest: Use AES GCM crypto library
>   virt: sev-guest: Move mutex to SNP guest device structure
>   virt: sev-guest: Replace pr_debug with dev_dbg
>   virt: sev-guest: Add SNP guest request structure
>   virt: sev-guest: Add vmpck_id to snp_guest_dev struct
>   x86/sev: Cache the secrets page address
>   x86/sev: Move and reorganize sev guest request api
>   x86/mm: Add generic guest initialization hook
>   x86/sev: Add Secure TSC support for SNP guests
>   x86/sev: Change TSC MSR behavior for Secure TSC enabled guests
>   x86/sev: Prevent RDTSC/RDTSCP interception for Secure TSC enabled
>     guests
>   x86/kvmclock: Skip kvmclock when Secure TSC is 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 +
>  arch/x86/include/asm/sev-guest.h        | 175 +++++++
>  arch/x86/include/asm/sev.h              |  19 +-
>  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                   | 631 +++++++++++++++++++++--
>  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 | 638 +++---------------------
>  drivers/virt/coco/sev-guest/sev-guest.h |  63 ---
>  include/linux/cc_platform.h             |   8 +
>  18 files changed, 882 insertions(+), 700 deletions(-)
>  create mode 100644 arch/x86/include/asm/sev-guest.h
>  delete mode 100644 drivers/virt/coco/sev-guest/sev-guest.h
> 
> 
> base-commit: 6995e2de6891c724bfeb2db33d7b87775f913ad1