This patch set adds support for the Intel flexible return and event delivery (FRED) architecture to allow Qemu to run KVM guests with FRED enabled. 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. 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 The counterpart KVM patch set is at: https://lore.kernel.org/kvm/20231108183003.5981-1-xin3.li@xxxxxxxxx/T/#m77876e22876f41c5ec677c0834a46113a4987d31 --- Changelog v3: - Add WRMSRNS as a baseline feature for FRED. - Add the secondary VM exit controls MSR. - Add FRED VMX controls to VM exit/entry feature words and scripts/kvm/vmxcap. - Do not set/get FRED SSP0 MSR, i.e. PL0_SSP MSR, with FRED, leave it to KVM CET. v2: - Add VMX nested-exception support to scripts/kvm/vmxcap (Paolo Bonzini). - Move FRED MSRs from basic x86_cpu part to .subsections part (Weijiang Yang). Xin Li (6): target/i386: add support for FRED in CPUID enumeration target/i386: mark CR4.FRED not reserved target/i386: add the secondary VM exit controls MSR target/i386: add support for VMX FRED controls target/i386: enumerate VMX nested-exception support target/i386: Add get/set/migrate support for FRED MSRs scripts/kvm/vmxcap | 13 ++++++++++++ target/i386/cpu.c | 15 ++++++++++--- target/i386/cpu.h | 42 ++++++++++++++++++++++++++++++++++++- target/i386/kvm/kvm.c | 49 +++++++++++++++++++++++++++++++++++++++++++ target/i386/machine.c | 28 +++++++++++++++++++++++++ 5 files changed, 143 insertions(+), 4 deletions(-) base-commit: a3c3aaa846ad61b801e7196482dcf4afb8ba34e4 -- 2.42.0
