This patch set enables the Intel flexible return and event delivery (FRED) architecture for x86-64. 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. 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" Changes since v8: * Move the FRED initialization patch after all required changes are in place (Thomas Gleixner). * Don't do syscall early out in fred_entry_from_user() before there are proper performance numbers and justifications (Thomas Gleixner). * Add the control exception handler to the FRED exception handler table (Thomas Gleixner). * Introduce a macro sysvec_install() to derive the asm handler name from a C handler, which simplifies the code and avoids an ugly typecast (Thomas Gleixner). * Remove junk code that assumes no local APIC on x86_64 (Thomas Gleixner). * Put IDTENTRY changes in a separate patch (Thomas Gleixner). * Use high-order 48 bits above the lowest 16 bit SS only when FRED is enabled (Thomas Gleixner). * Explain why writing directly to the IA32_KERNEL_GS_BASE MSR is doing the right thing (Thomas Gleixner). * Reword some patch descriptions (Thomas Gleixner). * Add a new macro VMX_DO_FRED_EVENT_IRQOFF for FRED instead of refactoring VMX_DO_EVENT_IRQOFF (Sean Christopherson). * Do NOT use a trampoline, just LEA+PUSH the return RIP, PUSH the error code, and jump to the FRED kernel entry point for NMI or call external_interrupt() for IRQs (Sean Christopherson). * Call external_interrupt() only when FRED is enabled, and convert the non-FRED handling to external_interrupt() after FRED lands (Sean Christopherson). * Use __packed instead of __attribute__((__packed__)) (Borislav Petkov). * Put all comments above the members, like the rest of the file does (Borislav Petkov). * Reflect the FRED spec 5.0 change that ERETS and ERETU add 8 to %rsp before popping the return context from the stack. * Reflect stack frame definition changes from FRED spec 3.0 to 5.0. * Add ENDBR to the FRED_ENTER asm macro after kernel IBT is added to FRED base line in FRED spec 5.0. * Add a document which briefly introduces FRED features. * Remove 2 patches, "allow FRED systems to use interrupt vectors 0x10-0x1f" and "allow dynamic stack frame size", from this patch set, as they are "optimizations" only. * Send 2 patches, "header file for event types" and "do not modify the DPL bits for a null selector", as pre-FRED patches. Changes since v7: * Always call external_interrupt() for VMX IRQ handling on x86_64, thus avoid re-entering the noinstr code. * Create a FRED stack frame when FRED is compiled-in but not enabled, which uses some extra stack space but simplifies the code. * Add a log message when FRED is enabled. Changes since v6: * Add a comment to explain why it is safe to write to a previous FRED stack frame. (Lai Jiangshan). * Export fred_entrypoint_kernel(), required when kvm-intel built as a module. * Reserve a REDZONE for CALL emulation and Align RSP to a 64-byte boundary before pushing a new FRED stack frame. * Replace pt_regs csx flags prefix FRED_CSL_ with FRED_CSX_. 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) (22): x86/fred: Add Kconfig option for FRED (CONFIG_X86_FRED) x86/fred: Disable FRED support if CONFIG_X86_FRED is disabled x86/cpufeatures: 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/cpu: Add MSR numbers for FRED configuration x86/fred: Make unions for the cs and ss fields in struct pt_regs x86/fred: Add a new header file for FRED definitions x86/fred: Reserve space for the FRED stack frame x86/fred: Update MSR_IA32_FRED_RSP0 during task switch x86/fred: Let ret_from_fork_asm() 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 task 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/traps: Add a system interrupt handler table for system interrupt dispatch x86/traps: Add external_interrupt() to dispatch external interrupts x86/fred: FRED entry/exit and dispatch code x86/fred: FRED initialization code Xin Li (14): Documentation/x86/64: Add documentation for FRED x86/fred: Define a common function type fred_handler x86/fred: Add a machine check entry stub for FRED x86/fred: Add a double fault entry stub for FRED x86/entry: Remove idtentry_sysvec from entry_{32,64}.S x86/idtentry: Incorporate definitions/declarations of the FRED external interrupt handler type x86/traps: Add sysvec_install() to install a system interrupt handler x86/idtentry: Incorporate declaration/definition of the FRED exception handler type x86/fred: Fixup fault on ERETU by jumping to fred_entrypoint_user x86/traps: Export external_interrupt() for handling IRQ in IRQ induced VM exits x86/fred: Export fred_entrypoint_kernel() for handling NMI in NMI induced VM exits KVM: VMX: Add VMX_DO_FRED_EVENT_IRQOFF for IRQ/NMI handling x86/syscall: Split IDT syscall setup code into idt_syscall_init() x86/fred: Disable FRED by default in its early stage .../admin-guide/kernel-parameters.txt | 4 + Documentation/arch/x86/x86_64/fred.rst | 102 ++++++++ Documentation/arch/x86/x86_64/index.rst | 1 + arch/x86/Kconfig | 9 + arch/x86/entry/Makefile | 5 +- arch/x86/entry/entry_32.S | 4 - arch/x86/entry/entry_64.S | 14 +- arch/x86/entry/entry_64_fred.S | 58 +++++ arch/x86/entry/entry_fred.c | 220 ++++++++++++++++++ arch/x86/entry/vsyscall/vsyscall_64.c | 2 +- arch/x86/include/asm/asm-prototypes.h | 1 + arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/disabled-features.h | 8 +- arch/x86/include/asm/extable_fixup_types.h | 4 +- arch/x86/include/asm/fred.h | 157 +++++++++++++ arch/x86/include/asm/idtentry.h | 115 ++++++++- arch/x86/include/asm/msr-index.h | 13 +- arch/x86/include/asm/ptrace.h | 57 ++++- arch/x86/include/asm/switch_to.h | 11 +- arch/x86/include/asm/thread_info.h | 12 +- arch/x86/include/asm/traps.h | 23 ++ arch/x86/include/uapi/asm/processor-flags.h | 2 + arch/x86/kernel/Makefile | 1 + arch/x86/kernel/cpu/acrn.c | 5 +- arch/x86/kernel/cpu/common.c | 47 +++- arch/x86/kernel/cpu/mce/core.c | 15 ++ arch/x86/kernel/cpu/mshyperv.c | 16 +- arch/x86/kernel/espfix_64.c | 8 + arch/x86/kernel/fred.c | 67 ++++++ arch/x86/kernel/irqinit.c | 7 +- arch/x86/kernel/kvm.c | 2 +- arch/x86/kernel/nmi.c | 19 ++ arch/x86/kernel/process_64.c | 31 ++- arch/x86/kernel/traps.c | 153 ++++++++++-- arch/x86/kvm/vmx/vmenter.S | 88 +++++++ arch/x86/kvm/vmx/vmx.c | 19 +- arch/x86/lib/x86-opcode-map.txt | 2 +- arch/x86/mm/extable.c | 79 +++++++ arch/x86/mm/fault.c | 18 +- drivers/xen/events/events_base.c | 3 +- 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 +- 45 files changed, 1348 insertions(+), 98 deletions(-) create mode 100644 Documentation/arch/x86/x86_64/fred.rst 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/fred.h create mode 100644 arch/x86/kernel/fred.c -- 2.34.1
