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Message-Id: <20230327075838.5403-22-xin3.li@intel.com> Date: Mon, 27 Mar 2023 00:58:26 -0700 From: Xin Li <xin3.li@...el.com> To: linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, peterz@...radead.org, andrew.cooper3@...rix.com, seanjc@...gle.com, pbonzini@...hat.com, ravi.v.shankar@...el.com, jiangshanlai@...il.com, shan.kang@...el.com Subject: [PATCH v6 21/33] x86/fred: FRED initialization code From: "H. Peter Anvin (Intel)" <hpa@...or.com> The code to initialize FRED when it's available and _not_ disabled. cpu_init_fred_exceptions() is the core function to initialize FRED, which 1. Sets up FRED entrypoints for events happening in ring 0 and 3. 2. Sets up a default stack for event handling. 3. Sets up dedicated event stacks for DB/NMI/MC/DF, equivalent to the IDT IST stacks. 4. Forces 32-bit system calls to use "int $0x80" only. 5. Enables FRED and invalidtes IDT. When the FRED is used, cpu_init_exception_handling() initializes FRED through calling cpu_init_fred_exceptions(), otherwise it sets up TSS IST and loads IDT. As FRED uses the ring 3 FRED entrypoint for SYSCALL and SYSENTER, it skips setting up SYSCALL/SYSENTER related MSRs, e.g., MSR_LSTAR. Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com> Co-developed-by: Xin Li <xin3.li@...el.com> Tested-by: Shan Kang <shan.kang@...el.com> Signed-off-by: Xin Li <xin3.li@...el.com> --- Changes since v5: * Add a comment for FRED stack level settings (Lai Jiangshan). --- arch/x86/include/asm/fred.h | 14 ++++++ arch/x86/include/asm/traps.h | 2 + arch/x86/kernel/Makefile | 1 + arch/x86/kernel/cpu/common.c | 74 ++++++++++++++++++++----------- arch/x86/kernel/fred.c | 86 ++++++++++++++++++++++++++++++++++++ arch/x86/kernel/irqinit.c | 7 ++- arch/x86/kernel/traps.c | 16 ++++++- 7 files changed, 170 insertions(+), 30 deletions(-) create mode 100644 arch/x86/kernel/fred.c diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h index 54746e8c0a17..cd974edc8e8a 100644 --- a/arch/x86/include/asm/fred.h +++ b/arch/x86/include/asm/fred.h @@ -99,8 +99,22 @@ DECLARE_FRED_HANDLER(fred_exc_debug); DECLARE_FRED_HANDLER(fred_exc_page_fault); DECLARE_FRED_HANDLER(fred_exc_machine_check); +/* + * The actual assembly entry and exit points + */ +extern __visible void fred_entrypoint_user(void); + +/* + * Initialization + */ +void cpu_init_fred_exceptions(void); +void fred_setup_apic(void); + #endif /* __ASSEMBLY__ */ +#else +#define cpu_init_fred_exceptions() BUG() +#define fred_setup_apic() BUG() #endif /* CONFIG_X86_FRED */ #endif /* ASM_X86_FRED_H */ diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index 46f5e4e2a346..612b3d6fec53 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -56,4 +56,6 @@ void __noreturn handle_stack_overflow(struct pt_regs *regs, void f (struct pt_regs *regs) typedef DECLARE_SYSTEM_INTERRUPT_HANDLER((*system_interrupt_handler)); +system_interrupt_handler get_system_interrupt_handler(unsigned int i); + #endif /* _ASM_X86_TRAPS_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index dd61752f4c96..08d9c0a0bfbe 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -47,6 +47,7 @@ obj-y += platform-quirks.o obj-y += process_$(BITS).o signal.o signal_$(BITS).o obj-y += traps.o idt.o irq.o irq_$(BITS).o dumpstack_$(BITS).o obj-y += time.o ioport.o dumpstack.o nmi.o +obj-$(CONFIG_X86_FRED) += fred.o obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o obj-y += setup.o x86_init.o i8259.o irqinit.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index e8cf6f4cfb52..eea41cb8722e 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -58,6 +58,7 @@ #include <asm/microcode_intel.h> #include <asm/intel-family.h> #include <asm/cpu_device_id.h> +#include <asm/fred.h> #include <asm/uv/uv.h> #include <asm/sigframe.h> #include <asm/traps.h> @@ -2054,28 +2055,6 @@ static void wrmsrl_cstar(unsigned long val) /* May not be marked __init: used by software suspend */ void syscall_init(void) { - wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS); - wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64); - -#ifdef CONFIG_IA32_EMULATION - wrmsrl_cstar((unsigned long)entry_SYSCALL_compat); - /* - * This only works on Intel CPUs. - * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EIP. - * This does not cause SYSENTER to jump to the wrong location, because - * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit). - */ - wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS); - wrmsrl_safe(MSR_IA32_SYSENTER_ESP, - (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1)); - wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat); -#else - wrmsrl_cstar((unsigned long)ignore_sysret); - wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); - wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); - wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); -#endif - /* * Flags to clear on syscall; clear as much as possible * to minimize user space-kernel interference. @@ -2086,6 +2065,41 @@ void syscall_init(void) X86_EFLAGS_IF|X86_EFLAGS_DF|X86_EFLAGS_OF| X86_EFLAGS_IOPL|X86_EFLAGS_NT|X86_EFLAGS_RF| X86_EFLAGS_AC|X86_EFLAGS_ID); + + /* + * The default user and kernel segments + */ + wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS); + + if (cpu_feature_enabled(X86_FEATURE_FRED)) { + /* Both sysexit and sysret cause #UD when FRED is enabled */ + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); + } else { + wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64); + +#ifdef CONFIG_IA32_EMULATION + wrmsrl_cstar((unsigned long)entry_SYSCALL_compat); + /* + * This only works on Intel CPUs. + * On AMD CPUs these MSRs are 32-bit, CPU truncates + * MSR_IA32_SYSENTER_EIP. + * This does not cause SYSENTER to jump to the wrong + * location, because AMD doesn't allow SYSENTER in + * long mode (either 32- or 64-bit). + */ + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, + (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1)); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat); +#else + wrmsrl_cstar((unsigned long)ignore_sysret); + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); +#endif + } } #else /* CONFIG_X86_64 */ @@ -2218,18 +2232,24 @@ void cpu_init_exception_handling(void) /* paranoid_entry() gets the CPU number from the GDT */ setup_getcpu(cpu); - /* IST vectors need TSS to be set up. */ - tss_setup_ist(tss); + /* Set up the TSS */ tss_setup_io_bitmap(tss); set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss); - load_TR_desc(); /* GHCB needs to be setup to handle #VC. */ setup_ghcb(); - /* Finally load the IDT */ - load_current_idt(); + if (cpu_feature_enabled(X86_FEATURE_FRED)) { + /* Set up FRED exception handling */ + cpu_init_fred_exceptions(); + } else { + /* IST vectors need TSS to be set up. */ + tss_setup_ist(tss); + + /* Finally load the IDT */ + load_current_idt(); + } } /* diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c new file mode 100644 index 000000000000..5b4272235f2e --- /dev/null +++ b/arch/x86/kernel/fred.c @@ -0,0 +1,86 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <linux/kernel.h> +#include <asm/desc.h> +#include <asm/fred.h> +#include <asm/tlbflush.h> /* For cr4_set_bits() */ +#include <asm/traps.h> + +/* + * Initialize FRED on this CPU. This cannot be __init as it is called + * during CPU hotplug. + */ +void cpu_init_fred_exceptions(void) +{ + wrmsrl(MSR_IA32_FRED_CONFIG, + FRED_CONFIG_ENTRYPOINT(fred_entrypoint_user) | + FRED_CONFIG_REDZONE(8) | /* Reserve for CALL emulation */ + FRED_CONFIG_INT_STKLVL(0)); + + /* + * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* + * (remember that user space faults are always taken on stack level 0) + * is to avoid overflowing the kernel stack. + * + * #DB in the kernel would imply the use of a kernel debugger. + * + * #DF is the highest level because a #DF means "something went wrong + * *while delivering an exception*." The number of cases for which that + * can happen with FRED is drastically reduced and basically amounts to + * "the stack you pointed me to is broken." Thus, always change stacks + * on #DF, which means it should be at the highest level. + */ + wrmsrl(MSR_IA32_FRED_STKLVLS, + FRED_STKLVL(X86_TRAP_DB, 1) | + FRED_STKLVL(X86_TRAP_NMI, 2) | + FRED_STKLVL(X86_TRAP_MC, 2) | + FRED_STKLVL(X86_TRAP_DF, 3)); + + /* The FRED equivalents to IST stacks... */ + wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); + wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); + wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); + + /* Not used with FRED */ + wrmsrl(MSR_LSTAR, 0ULL); + wrmsrl(MSR_CSTAR, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); + wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); + + /* Enable FRED */ + cr4_set_bits(X86_CR4_FRED); + idt_invalidate(); /* Any further IDT use is a bug */ + + /* Use int $0x80 for 32-bit system calls in FRED mode */ + setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); + setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); +} + +/* + * Initialize system vectors from a FRED perspective, so + * lapic_assign_system_vectors() can do its job. + */ +void __init fred_setup_apic(void) +{ + int i; + + for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) + set_bit(i, system_vectors); + + /* + * Don't set the non assigned system vectors in the + * system_vectors bitmap. Otherwise they show up in + * /proc/interrupts. + */ +#ifdef CONFIG_SMP + set_bit(IRQ_MOVE_CLEANUP_VECTOR, system_vectors); +#endif + + for (i = 0; i < NR_SYSTEM_VECTORS; i++) { + if (get_system_interrupt_handler(i) != NULL) { + set_bit(i + FIRST_SYSTEM_VECTOR, system_vectors); + } + } + + /* The rest are fair game... */ +} diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c index c683666876f1..2a510f72dd11 100644 --- a/arch/x86/kernel/irqinit.c +++ b/arch/x86/kernel/irqinit.c @@ -28,6 +28,7 @@ #include <asm/setup.h> #include <asm/i8259.h> #include <asm/traps.h> +#include <asm/fred.h> #include <asm/prom.h> /* @@ -96,7 +97,11 @@ void __init native_init_IRQ(void) /* Execute any quirks before the call gates are initialised: */ x86_init.irqs.pre_vector_init(); - idt_setup_apic_and_irq_gates(); + if (cpu_feature_enabled(X86_FEATURE_FRED)) + fred_setup_apic(); + else + idt_setup_apic_and_irq_gates(); + lapic_assign_system_vectors(); if (!acpi_ioapic && !of_ioapic && nr_legacy_irqs()) { diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 549f7f962f8f..ecfaf4d647bb 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -1537,6 +1537,14 @@ static system_interrupt_handler system_interrupt_handlers[NR_SYSTEM_VECTORS] = { #undef SYSV +system_interrupt_handler get_system_interrupt_handler(unsigned int i) +{ + if (i >= NR_SYSTEM_VECTORS) + return NULL; + + return system_interrupt_handlers[i]; +} + /* * External interrupt dispatch function. * @@ -1572,7 +1580,8 @@ void __init install_system_interrupt_handler(unsigned int n, const void *asm_add #ifdef CONFIG_X86_64 system_interrupt_handlers[n - FIRST_SYSTEM_VECTOR] = (system_interrupt_handler)addr; #endif - alloc_intr_gate(n, asm_addr); + if (!cpu_feature_enabled(X86_FEATURE_FRED)) + alloc_intr_gate(n, asm_addr); } void __init trap_init(void) @@ -1585,7 +1594,10 @@ void __init trap_init(void) /* Initialize TSS before setting up traps so ISTs work */ cpu_init_exception_handling(); + /* Setup traps as cpu_init() might #GP */ - idt_setup_traps(); + if (!cpu_feature_enabled(X86_FEATURE_FRED)) + idt_setup_traps(); + cpu_init(); } -- 2.34.1
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