This patch set enables FRED for x86-64. The Intel flexible return and event delivery (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. Search for the latest FRED spec in most search engines with this search pattern: site:intel.com FRED (flexible return and event delivery) specification As of now there is no publicly avaiable CPU supporting FRED, thus the Intel Simics® Simulator is used as software development and testing vehicles. And it can be downloaded from: https://www.intel.com/content/www/us/en/developer/articles/tool/simics-simulator.html To enable FRED, the Simics package 8112 QSP-CPU needs to be installed with CPU model configured as: $cpu_comp_class = "x86-experimental-fred" Longer term, we should refactor common code shared by FRED and IDT into common shared files, and contain IDT code using a new config CONFIG_X86_IDT. Changes since v5: * Initialize system_interrupt_handlers with dispatch_table_spurious_interrupt() instead of NULL to get rid of a branch (Peter Zijlstra). * Disallow #DB inside #MCE for robustness sake (Peter Zijlstra). * Add a comment for FRED stack level settings (Lai Jiangshan). * Move the NMI bit from an invalid stack frame, which caused ERETU to fault, to the fault handler's stack frame, thus to unblock NMI ASAP if NMI is blocked (Lai Jiangshan). * Refactor VMX_DO_EVENT_IRQOFF to handle IRQ/NMI in IRQ/NMI induced VM exits when FRED is enabled (Sean Christopherson). Changes since v4: * Do NOT use the term "injection", which in the KVM context means to reinject an event into the guest (Sean Christopherson). * Add the explanation of why to execute "int $2" to invoke the NMI handler in NMI caused VM exits (Sean Christopherson). * Use cs/ss instead of csx/ssx when initializing the pt_regs structure for calling external_interrupt(), otherwise it breaks i386 build. Changes since v3: * Call external_interrupt() to handle IRQ in IRQ caused VM exits. * Execute "int $2" to handle NMI in NMI caused VM exits. * Rename csl/ssl of the pt_regs structure to csx/ssx (x for extended) (Andrew Cooper). Changes since v2: * Improve comments for changes in arch/x86/include/asm/idtentry.h. Changes since v1: * call irqentry_nmi_{enter,exit}() in both IDT and FRED debug fault kernel handler (Peter Zijlstra). * Initialize a FRED exception handler to fred_bad_event() instead of NULL if no FRED handler defined for an exception vector (Peter Zijlstra). * Push calling irqentry_{enter,exit}() and instrumentation_{begin,end}() down into individual FRED exception handlers, instead of in the dispatch framework (Peter Zijlstra). H. Peter Anvin (Intel) (24): x86/traps: let common_interrupt() handle IRQ_MOVE_CLEANUP_VECTOR x86/fred: make unions for the cs and ss fields in struct pt_regs x86/traps: add a system interrupt table for system interrupt dispatch x86/traps: add external_interrupt() to dispatch external interrupts x86/cpufeature: add the cpu feature bit for FRED x86/opcode: add ERETU, ERETS instructions to x86-opcode-map x86/objtool: teach objtool about ERETU and ERETS x86/cpu: add X86_CR4_FRED macro x86/fred: add Kconfig option for FRED (CONFIG_X86_FRED) x86/fred: if CONFIG_X86_FRED is disabled, disable FRED support x86/cpu: add MSR numbers for FRED configuration x86/fred: header file with FRED definitions x86/fred: reserve space for the FRED stack frame x86/fred: add a page fault entry stub for FRED x86/fred: add a debug fault entry stub for FRED x86/fred: add a NMI entry stub for FRED x86/fred: FRED entry/exit and dispatch code x86/fred: FRED initialization code x86/fred: update MSR_IA32_FRED_RSP0 during task switch x86/fred: let ret_from_fork() jmp to fred_exit_user when FRED is enabled x86/fred: disallow the swapgs instruction when FRED is enabled x86/fred: no ESPFIX needed when FRED is enabled x86/fred: allow single-step trap and NMI when starting a new thread x86/fred: allow FRED systems to use interrupt vectors 0x10-0x1f Xin Li (9): x86/traps: add install_system_interrupt_handler() x86/fred: header file for event types x86/fred: add a machine check entry stub for FRED x86/fred: fixup fault on ERETU by jumping to fred_entrypoint_user x86/ia32: do not modify the DPL bits for a null selector x86/fred: allow dynamic stack frame size x86/fred: BUG() when ERETU with %rsp not equal to that when the ring 3 event was just delivered x86/fred: disable FRED by default in its early stage KVM: x86/vmx: refactor VMX_DO_EVENT_IRQOFF to generate FRED stack frames .../admin-guide/kernel-parameters.txt | 4 + arch/x86/Kconfig | 9 + arch/x86/entry/Makefile | 5 +- arch/x86/entry/entry_32.S | 2 +- arch/x86/entry/entry_64.S | 5 + arch/x86/entry/entry_64_fred.S | 61 +++++ arch/x86/entry/entry_fred.c | 234 ++++++++++++++++++ arch/x86/entry/vsyscall/vsyscall_64.c | 2 +- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/disabled-features.h | 8 +- arch/x86/include/asm/entry-common.h | 3 + arch/x86/include/asm/event-type.h | 17 ++ arch/x86/include/asm/extable_fixup_types.h | 4 +- arch/x86/include/asm/fred.h | 131 ++++++++++ arch/x86/include/asm/idtentry.h | 76 +++++- arch/x86/include/asm/irq.h | 5 + arch/x86/include/asm/irq_vectors.h | 15 +- arch/x86/include/asm/msr-index.h | 13 +- arch/x86/include/asm/processor.h | 12 +- arch/x86/include/asm/ptrace.h | 34 ++- arch/x86/include/asm/switch_to.h | 10 +- arch/x86/include/asm/thread_info.h | 35 +-- arch/x86/include/asm/traps.h | 13 + arch/x86/include/asm/vmx.h | 17 +- arch/x86/include/uapi/asm/processor-flags.h | 2 + arch/x86/kernel/Makefile | 1 + arch/x86/kernel/apic/apic.c | 11 +- arch/x86/kernel/apic/vector.c | 8 +- arch/x86/kernel/cpu/acrn.c | 7 +- arch/x86/kernel/cpu/common.c | 88 ++++--- arch/x86/kernel/cpu/mce/core.c | 15 ++ arch/x86/kernel/cpu/mshyperv.c | 22 +- arch/x86/kernel/espfix_64.c | 8 + arch/x86/kernel/fred.c | 86 +++++++ arch/x86/kernel/head_32.S | 3 +- arch/x86/kernel/idt.c | 6 +- arch/x86/kernel/irq.c | 6 +- arch/x86/kernel/irqinit.c | 7 +- arch/x86/kernel/kvm.c | 4 +- arch/x86/kernel/nmi.c | 19 ++ arch/x86/kernel/process.c | 5 + arch/x86/kernel/process_64.c | 21 +- arch/x86/kernel/signal_32.c | 21 +- arch/x86/kernel/traps.c | 175 +++++++++++-- arch/x86/kvm/vmx/vmenter.S | 59 ++++- arch/x86/kvm/vmx/vmx.c | 8 +- arch/x86/lib/x86-opcode-map.txt | 2 +- arch/x86/mm/extable.c | 44 ++++ arch/x86/mm/fault.c | 20 +- drivers/xen/events/events_base.c | 5 +- kernel/fork.c | 6 + tools/arch/x86/include/asm/cpufeatures.h | 1 + .../arch/x86/include/asm/disabled-features.h | 8 +- tools/arch/x86/include/asm/msr-index.h | 13 +- tools/arch/x86/lib/x86-opcode-map.txt | 2 +- tools/objtool/arch/x86/decode.c | 19 +- 56 files changed, 1242 insertions(+), 176 deletions(-) create mode 100644 arch/x86/entry/entry_64_fred.S create mode 100644 arch/x86/entry/entry_fred.c create mode 100644 arch/x86/include/asm/event-type.h create mode 100644 arch/x86/include/asm/fred.h create mode 100644 arch/x86/kernel/fred.c -- 2.34.1
