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x86/idt: Rework IDT setup for boot CPU
A basic IDT setup for the boot CPU has to be done before invoking cpu_init() because that might trigger #GP when accessing certain MSRs. This setup cannot install the IST variants on 64-bit because the TSS setup which is required for ISTs to work happens in cpu_init(). That leaves a theoretical window where a NMI would invoke the ASM entry point which relies on IST being enabled on the kernel stack which is undefined behaviour. This setup logic has never worked correctly, but on the other hand a NMI hitting the boot CPU before it has fully set up the IDT would be fatal anyway. So the small window between the wrong NMI gate and the IST based NMI gate is not really adding a substantial amount of risk. But the setup logic is nevertheless more convoluted than necessary. The recent separation of the TSS setup into a separate function to ensure that setup so it can setup TSS first, then initialize IDT with the IST variants before invoking cpu_init() and get rid of the post cpu_init() IST setup. Move the invocation of cpu_init_exception_handling() ahead of idt_setup_traps() and merge the IST setup into the default setup table. Reported-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Lai Jiangshan <laijs@linux.alibaba.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210507114000.569244755@linutronix.de
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3 changed files with 15 additions and 34 deletions
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@ -421,10 +421,8 @@ extern bool idt_is_f00f_address(unsigned long address);
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#ifdef CONFIG_X86_64
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extern void idt_setup_early_pf(void);
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extern void idt_setup_ist_traps(void);
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#else
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static inline void idt_setup_early_pf(void) { }
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static inline void idt_setup_ist_traps(void) { }
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#endif
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extern void idt_invalidate(void *addr);
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@ -35,12 +35,16 @@
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#define SYSG(_vector, _addr) \
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G(_vector, _addr, DEFAULT_STACK, GATE_INTERRUPT, DPL3, __KERNEL_CS)
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#ifdef CONFIG_X86_64
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/*
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* Interrupt gate with interrupt stack. The _ist index is the index in
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* the tss.ist[] array, but for the descriptor it needs to start at 1.
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*/
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#define ISTG(_vector, _addr, _ist) \
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G(_vector, _addr, _ist + 1, GATE_INTERRUPT, DPL0, __KERNEL_CS)
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#else
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#define ISTG(_vector, _addr, _ist) INTG(_vector, _addr)
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#endif
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/* Task gate */
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#define TSKG(_vector, _gdt) \
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@ -74,7 +78,7 @@ static const __initconst struct idt_data early_idts[] = {
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*/
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static const __initconst struct idt_data def_idts[] = {
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INTG(X86_TRAP_DE, asm_exc_divide_error),
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INTG(X86_TRAP_NMI, asm_exc_nmi),
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ISTG(X86_TRAP_NMI, asm_exc_nmi, IST_INDEX_NMI),
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INTG(X86_TRAP_BR, asm_exc_bounds),
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INTG(X86_TRAP_UD, asm_exc_invalid_op),
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INTG(X86_TRAP_NM, asm_exc_device_not_available),
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@ -91,12 +95,16 @@ static const __initconst struct idt_data def_idts[] = {
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#ifdef CONFIG_X86_32
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TSKG(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS),
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#else
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INTG(X86_TRAP_DF, asm_exc_double_fault),
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ISTG(X86_TRAP_DF, asm_exc_double_fault, IST_INDEX_DF),
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#endif
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INTG(X86_TRAP_DB, asm_exc_debug),
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ISTG(X86_TRAP_DB, asm_exc_debug, IST_INDEX_DB),
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#ifdef CONFIG_X86_MCE
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INTG(X86_TRAP_MC, asm_exc_machine_check),
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ISTG(X86_TRAP_MC, asm_exc_machine_check, IST_INDEX_MCE),
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#endif
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#ifdef CONFIG_AMD_MEM_ENCRYPT
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ISTG(X86_TRAP_VC, asm_exc_vmm_communication, IST_INDEX_VC),
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#endif
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SYSG(X86_TRAP_OF, asm_exc_overflow),
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@ -221,22 +229,6 @@ static const __initconst struct idt_data early_pf_idts[] = {
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INTG(X86_TRAP_PF, asm_exc_page_fault),
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};
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/*
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* The exceptions which use Interrupt stacks. They are setup after
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* cpu_init() when the TSS has been initialized.
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*/
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static const __initconst struct idt_data ist_idts[] = {
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ISTG(X86_TRAP_DB, asm_exc_debug, IST_INDEX_DB),
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ISTG(X86_TRAP_NMI, asm_exc_nmi, IST_INDEX_NMI),
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ISTG(X86_TRAP_DF, asm_exc_double_fault, IST_INDEX_DF),
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#ifdef CONFIG_X86_MCE
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ISTG(X86_TRAP_MC, asm_exc_machine_check, IST_INDEX_MCE),
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#endif
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#ifdef CONFIG_AMD_MEM_ENCRYPT
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ISTG(X86_TRAP_VC, asm_exc_vmm_communication, IST_INDEX_VC),
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#endif
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};
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/**
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* idt_setup_early_pf - Initialize the idt table with early pagefault handler
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*
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@ -254,14 +246,6 @@ void __init idt_setup_early_pf(void)
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idt_setup_from_table(idt_table, early_pf_idts,
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ARRAY_SIZE(early_pf_idts), true);
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}
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/**
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* idt_setup_ist_traps - Initialize the idt table with traps using IST
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*/
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void __init idt_setup_ist_traps(void)
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{
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idt_setup_from_table(idt_table, ist_idts, ARRAY_SIZE(ist_idts), true);
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}
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#endif
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static void __init idt_map_in_cea(void)
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@ -1160,10 +1160,9 @@ void __init trap_init(void)
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/* Init GHCB memory pages when running as an SEV-ES guest */
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sev_es_init_vc_handling();
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idt_setup_traps();
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/* Initialize TSS before setting up traps so ISTs work */
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cpu_init_exception_handling();
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/* Setup traps as cpu_init() might #GP */
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idt_setup_traps();
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cpu_init();
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idt_setup_ist_traps();
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}
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