Re: [PATCH v7 00/16] Add Secure TSC support for SNP guests

[Dionna Amalie Glaze]

On Wed, Jan 24, 2024 at 10:08 PM Nikunj A. Dadhania <nikunj@xxxxxxx> wrote:
>
> On 12/20/2023 8:43 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:
> > 01-08: Preparation and movement of sev-guest driver code
> > 09-16: SecureTSC enablement patches.
> >
> > Testing SecureTSC
> > -----------------
> >
> > SecureTSC hypervisor patches based on top of SEV-SNP Guest MEMFD series:
> > https://github.com/nikunjad/linux/tree/snp-host-latest-securetsc_v5
> >
> > QEMU changes:
> > https://github.com/nikunjad/qemu/tree/snp_securetsc_v5
> >
> > QEMU commandline SEV-SNP-UPM with SecureTSC:
> >
> >   qemu-system-x86_64 -cpu EPYC-Milan-v2,+secure-tsc,+invtsc -smp 4 \
> >     -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=snp \
> >     ...
> >
> > Changelog:
> > ----------
> > v7:
> > * Drop mutex from the snp_dev and add snp_guest_cmd_{lock,unlock} API
> > * Added comments for secrets page failure
> > * Added define for maximum supported VMPCK
> > * Updated comments why sev_status is used directly instead of
> >   cpu_feature_enabled()
>
> A gentle reminder.
>

>From the Google testing side of things, we may not get to this for
another while.

> Regards
> Nikunj
>


-- 
-Dionna Glaze, PhD (she/her)