[PATCH 0/7] KVM: SVM: Enable FRED support

[Shivansh Dhiman <shivansh.dhiman@amd.com>]

This series adds SVM support for FRED (Flexible Return and Event Delivery)
virtualization in KVM.

FRED introduces simplified privilege level transitions to replace IDT-based
event delivery and IRET returns, providing lower latency event handling while
ensuring complete supervisor context on delivery and full user context on
return. FRED defines event delivery for both ring 3->0 and ring 0->0
transitions, and introduces ERETU for returning to ring 3 and ERETS for
remaining in ring 0.

AMD hardware extends the VMCB to support FRED virtualization with dedicated
save area fields for FRED MSRs (RSP0-3, SSP1-3, STKLVLS, CONFIG) and control
fields for event injection data (EXITINTDATA, EVENTINJDATA).

The implementation spans seven patches. The important changes are:

1) Extend VMCB structures with FRED fields mentioned above and disable MSR
   interception for FRED-enabled guests to avoid unnecessary VM exits.

2) Support for nested exceptions where we populate event injection data
   when delivering exceptions like page faults and debug traps. 

This series is based on top of FRED support for VMX patchset [1],
patches 1-17. The VMX patchset was rebased on top of v6.18.0 kernel.

[1] https://lore.kernel.org/kvm/20251026201911.505204-1-xin@zytor.com

Regards,
Shivansh
---
Neeraj Upadhyay (5):
  KVM: SVM: Initialize FRED VMCB fields
  KVM: SVM: Disable interception of FRED MSRs for FRED supported guests
  KVM: SVM: Save restore FRED_RSP0 for FRED supported guests
  KVM: SVM: Populate FRED event data on event injection
  KVM: SVM: Support FRED nested exception injection

Shivansh Dhiman (2):
  KVM: SVM: Dump FRED context in dump_vmcb()
  KVM: SVM: Enable save/restore of FRED MSRs

 arch/x86/include/asm/svm.h |  35 ++++++++++-
 arch/x86/kvm/svm/svm.c     | 116 +++++++++++++++++++++++++++++++++++--
 2 files changed, 144 insertions(+), 7 deletions(-)


base-commit: f76e83ecf6bce6d3793f828d92170b69e636f3c9
-- 
2.43.0