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 major changes are: 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 The first 20 patches add FRED support to VMX, and the rest 7 patches add FRED support to nested VMX. Following is the link to the v2 of this patch set: https://lore.kernel.org/kvm/20240207172646.3981-1-xin3.li@xxxxxxxxx/ Sean Christopherson (3): KVM: x86: Use a dedicated flow for queueing re-injected exceptions KVM: VMX: Don't modify guest XFD_ERR if CR0.TS=1 KVM: VMX: Pass XFD_ERR as pseudo-payload when injecting #NM Xin Li (21): KVM: VMX: Add support for the secondary VM exit controls KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config KVM: VMX: Disable FRED if FRED consistency checks fail KVM: VMX: Initialize VMCS FRED fields KVM: x86: Use KVM-governed feature framework to track "FRED enabled" KVM: VMX: Set FRED MSR interception KVM: VMX: Save/restore guest FRED RSP0 KVM: VMX: Add support for FRED context save/restore KVM: x86: Add a helper to detect if FRED is enabled for a vCPU KVM: VMX: Virtualize FRED event_data KVM: VMX: Virtualize FRED nested exception tracking KVM: x86: Mark CR4.FRED as not reserved when guest can use FRED KVM: VMX: Dump FRED context in dump_vmcs() KVM: x86: Allow FRED/LKGS to be advertised to guests KVM: x86: Allow WRMSRNS to be advertised to guests KVM: VMX: Invoke vmx_set_cpu_caps() before nested setup KVM: nVMX: Add support for the secondary VM exit controls KVM: nVMX: Add a prerequisite to SHADOW_FIELD_R[OW] macros KVM: nVMX: Add FRED VMCS fields KVM: nVMX: Add VMCS FRED states checking KVM: nVMX: Allow VMX FRED controls Xin Li (Intel) (3): x86/cea: Export per CPU variable cea_exception_stacks KVM: VMX: Do not use MAX_POSSIBLE_PASSTHROUGH_MSRS in array definition KVM: nVMX: Add a prerequisite to existence of VMCS fields Documentation/virt/kvm/x86/nested-vmx.rst | 19 ++ arch/x86/include/asm/kvm_host.h | 9 +- arch/x86/include/asm/msr-index.h | 1 + arch/x86/include/asm/vmx.h | 32 ++- arch/x86/kvm/cpuid.c | 4 +- arch/x86/kvm/governed_features.h | 1 + arch/x86/kvm/kvm_cache_regs.h | 15 ++ arch/x86/kvm/svm/svm.c | 15 +- arch/x86/kvm/vmx/capabilities.h | 17 +- arch/x86/kvm/vmx/nested.c | 291 ++++++++++++++++---- arch/x86/kvm/vmx/nested.h | 8 + arch/x86/kvm/vmx/nested_vmcs_fields.h | 25 ++ 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 | 37 ++- arch/x86/kvm/vmx/vmx.c | 308 +++++++++++++++++++--- arch/x86/kvm/vmx/vmx.h | 15 +- arch/x86/kvm/x86.c | 140 ++++++---- arch/x86/kvm/x86.h | 8 +- arch/x86/mm/cpu_entry_area.c | 1 + 21 files changed, 846 insertions(+), 158 deletions(-) create mode 100644 arch/x86/kvm/vmx/nested_vmcs_fields.h base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc -- 2.46.2
