On Tue, Nov 28, 2023 at 6:00 AM Nikunj A Dadhania <nikunj@xxxxxxx> 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 \ > ... Thanks Nikunj! I was able to modify my SNP host kernel to support SecureTSC based off of your `snp-host-latest-securetsc_v5` and use that to test this series. Seemed to work as intended in the happy path but I didn't spend much time trying any corner cases. Also checked the series continues to work without SecureTSC enabled for the V. Tested-by: Peter Gonda <pgonda@xxxxxxxxxx>
