linux-kernel - Re: [PATCH v4 00/14] Add Secure TSC support for SNP guests

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Date:   Mon, 28 Aug 2023 09:17:23 +0530
From:   "Nikunj A. Dadhania" <nikunj@....com>
To:     thomas.lendacky@....com, x86@...nel.org
Cc:     dionnaglaze@...gle.com, pgonda@...gle.com, seanjc@...gle.com,
        pbonzini@...hat.com, bp@...en8.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 00/14] Add Secure TSC support for SNP guests

On 8/14/2023 11:22 AM, 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.
> 
> 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:
> ----------
> v4:
> * Drop handle_guest_request() and handle_guest_request_ext()
> * Drop NULL check for key
> * Corrected commit subject
> * Added Reviewed-by from Tom

A gentle reminder.

Regards
Nikunj