[PATCH v1 00/23] Enable FRED with KVM VMX

Xin Li
2023-11-08T19:00:18Z

This patch set enables the Intel flexible return and event delivery
(FRED) architecture with KVM VMX to allow guests to utilize FRED.

The FRED architecture defines simple new transitions that change
privilege level (ring transitions). The FRED architecture was
designed with the following goals:

1) Improve overall performance and response time by replacing event
delivery through the interrupt descriptor table (IDT event
delivery) and event return by the IRET instruction with lower
latency transitions.

2) Improve software robustness by ensuring that event delivery
establishes the full supervisor context and that event return
establishes the full user context.

The new transitions defined by the FRED architecture are FRED event
delivery and, for returning from events, two FRED return instructions.
FRED event delivery can effect a transition from ring 3 to ring 0, but
it is used also to deliver events incident to ring 0. One FRED
instruction (ERETU) effects a return from ring 0 to ring 3, while the
other (ERETS) returns while remaining in ring 0. Collectively, FRED
event delivery and the FRED return instructions are FRED transitions.

Intel VMX architecture is extended to run FRED guests, and the changes
are majorly:

1) New VMCS fields for FRED context management, which includes two new
event data VMCS fields, eight new guest FRED context VMCS fields and
eight new host FRED context VMCS fields.

2) VMX nested-Exception support for proper virtualization of stack
levels introduced with FRED architecture.

Search for the latest FRED spec in most search engines with this search pattern:

site:intel.com FRED (flexible return and event delivery) specification

We want to send out the FRED VMX patch set for review while the FRED
native patch set v12 is being reviewed @
https://lkml.kernel.org/kvm/20231003062458.23552-1-xin3.li@intel.com/.
For easier review, I have set up a base tree with the latest FRED native
patch set on top of tip tree in the 'fred_v12' branch of repo
https://github.com/xinli-intel/linux-fred-public.git.

Patch 1-2 are cleanups to VMX basic and misc MSRs, which were sent
out earlier as a preparation for FRED changes:
https://lore.kernel.org/kvm/20231030233940.438233-1-xin@zytor.com/.

Patch 3-14 add FRED support to VMX.
Patch 15-18 add FRED support to nested VMX.
Patch 19 exposes FRED to KVM guests to complete the enabling.
Patch 20-23 adds FRED selftests.

Shan Kang (1):
KVM: selftests: Add fred exception tests

Xin Li (22):
KVM: VMX: Cleanup VMX basic information defines and usages
KVM: VMX: Cleanup VMX misc information defines and usages
KVM: VMX: Add support for the secondary VM exit controls
KVM: x86: Mark CR4.FRED as not reserved
KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config
KVM: VMX: Defer enabling FRED MSRs save/load until after set CPUID
KVM: VMX: Disable intercepting FRED MSRs
KVM: VMX: Initialize VMCS FRED fields
KVM: VMX: Switch FRED RSP0 between host and guest
KVM: VMX: Add support for FRED context save/restore
KVM: x86: Add kvm_is_fred_enabled()
KVM: VMX: Handle FRED event data
KVM: VMX: Handle VMX nested exception for FRED
KVM: VMX: Dump FRED context in dump_vmcs()
KVM: nVMX: Add support for the secondary VM exit controls
KVM: nVMX: Add FRED VMCS fields
KVM: nVMX: Add support for VMX FRED controls
KVM: nVMX: Add VMCS FRED states checking
KVM: x86: Allow FRED/LKGS/WRMSRNS to be exposed to guests
KVM: selftests: Add FRED VMCS fields to evmcs
KVM: selftests: Run debug_regs test with FRED enabled
KVM: selftests: Add a new VM guest mode to run user level code

Documentation/virt/kvm/x86/nested-vmx.rst | 19 +
arch/x86/include/asm/hyperv-tlfs.h | 19 +
arch/x86/include/asm/kvm_host.h | 9 +-
arch/x86/include/asm/msr-index.h | 15 +-
arch/x86/include/asm/vmx.h | 57 ++-
arch/x86/kvm/cpuid.c | 4 +-
arch/x86/kvm/kvm_cache_regs.h | 10 +
arch/x86/kvm/svm/svm.c | 4 +-
arch/x86/kvm/vmx/capabilities.h | 20 +-
arch/x86/kvm/vmx/hyperv.c | 61 ++-
arch/x86/kvm/vmx/nested.c | 315 ++++++++++++--
arch/x86/kvm/vmx/nested.h | 2 +-
arch/x86/kvm/vmx/vmcs.h | 1 +
arch/x86/kvm/vmx/vmcs12.c | 19 +
arch/x86/kvm/vmx/vmcs12.h | 38 ++
arch/x86/kvm/vmx/vmcs_shadow_fields.h | 6 +-
arch/x86/kvm/vmx/vmx.c | 404 ++++++++++++++++--
arch/x86/kvm/vmx/vmx.h | 14 +-
arch/x86/kvm/x86.c | 55 ++-
arch/x86/kvm/x86.h | 5 +-
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/include/kvm_util_base.h | 1 +
.../selftests/kvm/include/x86_64/evmcs.h | 146 +++++++
.../selftests/kvm/include/x86_64/processor.h | 33 ++
.../selftests/kvm/include/x86_64/vmx.h | 20 +
tools/testing/selftests/kvm/lib/kvm_util.c | 5 +-
.../selftests/kvm/lib/x86_64/processor.c | 15 +-
tools/testing/selftests/kvm/lib/x86_64/vmx.c | 4 +-
.../testing/selftests/kvm/x86_64/debug_regs.c | 50 ++-
.../testing/selftests/kvm/x86_64/fred_test.c | 262 ++++++++++++
30 files changed, 1464 insertions(+), 150 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/fred_test.c

base-commit: d49b86c24e836941c85c4906e9519fca9426a6e0
--
2.42.0