From: Thomas Gleixner tglx@linutronix.de
commit f8a8fe61fec8006575699559ead88b0b833d5cad upstream.
Quite some time ago the interrupt entry stubs for unused vectors in the system vector range got removed and directly mapped to the spurious interrupt vector entry point.
Sounds reasonable, but it's subtly broken. The spurious interrupt vector entry point pushes vector number 0xFF on the stack which makes the whole logic in __smp_spurious_interrupt() pointless.
As a consequence any spurious interrupt which comes from a vector != 0xFF is treated as a real spurious interrupt (vector 0xFF) and not acknowledged. That subsequently stalls all interrupt vectors of equal and lower priority, which brings the system to a grinding halt.
This can happen because even on 64-bit the system vector space is not guaranteed to be fully populated. A full compile time handling of the unused vectors is not possible because quite some of them are conditonally populated at runtime.
Bring the entry stubs back, which wastes 160 bytes if all stubs are unused, but gains the proper handling back. There is no point to selectively spare some of the stubs which are known at compile time as the required code in the IDT management would be way larger and convoluted.
Do not route the spurious entries through common_interrupt and do_IRQ() as the original code did. Route it to smp_spurious_interrupt() which evaluates the vector number and acts accordingly now that the real vector numbers are handed in.
Fixup the pr_warn so the actual spurious vector (0xff) is clearly distiguished from the other vectors and also note for the vectored case whether it was pending in the ISR or not.
"Spurious APIC interrupt (vector 0xFF) on CPU#0, should never happen." "Spurious interrupt vector 0xed on CPU#1. Acked." "Spurious interrupt vector 0xee on CPU#1. Not pending!."
Fixes: 2414e021ac8d ("x86: Avoid building unused IRQ entry stubs") Reported-by: Jan Kiszka jan.kiszka@siemens.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Marc Zyngier marc.zyngier@arm.com Cc: Jan Beulich jbeulich@suse.com Link: https://lkml.kernel.org/r/20190628111440.550568228@linutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/entry/entry_32.S | 24 ++++++++++++++++++++++++ arch/x86/entry/entry_64.S | 30 ++++++++++++++++++++++++++---- arch/x86/include/asm/hw_irq.h | 2 ++ arch/x86/kernel/apic/apic.c | 33 ++++++++++++++++++++++----------- arch/x86/kernel/idt.c | 3 ++- 5 files changed, 76 insertions(+), 16 deletions(-)
--- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1105,6 +1105,30 @@ ENTRY(irq_entries_start) .endr END(irq_entries_start)
+#ifdef CONFIG_X86_LOCAL_APIC + .align 8 +ENTRY(spurious_entries_start) + vector=FIRST_SYSTEM_VECTOR + .rept (NR_VECTORS - FIRST_SYSTEM_VECTOR) + pushl $(~vector+0x80) /* Note: always in signed byte range */ + vector=vector+1 + jmp common_spurious + .align 8 + .endr +END(spurious_entries_start) + +common_spurious: + ASM_CLAC + addl $-0x80, (%esp) /* Adjust vector into the [-256, -1] range */ + SAVE_ALL switch_stacks=1 + ENCODE_FRAME_POINTER + TRACE_IRQS_OFF + movl %esp, %eax + call smp_spurious_interrupt + jmp ret_from_intr +ENDPROC(common_interrupt) +#endif + /* * the CPU automatically disables interrupts when executing an IRQ vector, * so IRQ-flags tracing has to follow that: --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -377,6 +377,18 @@ ENTRY(irq_entries_start) .endr END(irq_entries_start)
+ .align 8 +ENTRY(spurious_entries_start) + vector=FIRST_SYSTEM_VECTOR + .rept (NR_VECTORS - FIRST_SYSTEM_VECTOR) + UNWIND_HINT_IRET_REGS + pushq $(~vector+0x80) /* Note: always in signed byte range */ + jmp common_spurious + .align 8 + vector=vector+1 + .endr +END(spurious_entries_start) + .macro DEBUG_ENTRY_ASSERT_IRQS_OFF #ifdef CONFIG_DEBUG_ENTRY pushq %rax @@ -573,10 +585,20 @@ _ASM_NOKPROBE(interrupt_entry)
/* Interrupt entry/exit. */
- /* - * The interrupt stubs push (~vector+0x80) onto the stack and - * then jump to common_interrupt. - */ +/* + * The interrupt stubs push (~vector+0x80) onto the stack and + * then jump to common_spurious/interrupt. + */ +common_spurious: + addq $-0x80, (%rsp) /* Adjust vector to [-256, -1] range */ + call interrupt_entry + UNWIND_HINT_REGS indirect=1 + call smp_spurious_interrupt /* rdi points to pt_regs */ + jmp ret_from_intr +END(common_spurious) +_ASM_NOKPROBE(common_spurious) + +/* common_interrupt is a hotpath. Align it */ .p2align CONFIG_X86_L1_CACHE_SHIFT common_interrupt: addq $-0x80, (%rsp) /* Adjust vector to [-256, -1] range */ --- a/arch/x86/include/asm/hw_irq.h +++ b/arch/x86/include/asm/hw_irq.h @@ -150,6 +150,8 @@ extern char irq_entries_start[]; #define trace_irq_entries_start irq_entries_start #endif
+extern char spurious_entries_start[]; + #define VECTOR_UNUSED NULL #define VECTOR_SHUTDOWN ((void *)~0UL) #define VECTOR_RETRIGGERED ((void *)~1UL) --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -2035,21 +2035,32 @@ __visible void __irq_entry smp_spurious_ entering_irq(); trace_spurious_apic_entry(vector);
+ inc_irq_stat(irq_spurious_count); + + /* + * If this is a spurious interrupt then do not acknowledge + */ + if (vector == SPURIOUS_APIC_VECTOR) { + /* See SDM vol 3 */ + pr_info("Spurious APIC interrupt (vector 0xFF) on CPU#%d, should never happen.\n", + smp_processor_id()); + goto out; + } + /* - * Check if this really is a spurious interrupt and ACK it - * if it is a vectored one. Just in case... - * Spurious interrupts should not be ACKed. + * If it is a vectored one, verify it's set in the ISR. If set, + * acknowledge it. */ v = apic_read(APIC_ISR + ((vector & ~0x1f) >> 1)); - if (v & (1 << (vector & 0x1f))) + if (v & (1 << (vector & 0x1f))) { + pr_info("Spurious interrupt (vector 0x%02x) on CPU#%d. Acked\n", + vector, smp_processor_id()); ack_APIC_irq(); - - inc_irq_stat(irq_spurious_count); - - /* see sw-dev-man vol 3, chapter 7.4.13.5 */ - pr_info("spurious APIC interrupt through vector %02x on CPU#%d, " - "should never happen.\n", vector, smp_processor_id()); - + } else { + pr_info("Spurious interrupt (vector 0x%02x) on CPU#%d. Not pending!\n", + vector, smp_processor_id()); + } +out: trace_spurious_apic_exit(vector); exiting_irq(); } --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -321,7 +321,8 @@ void __init idt_setup_apic_and_irq_gates #ifdef CONFIG_X86_LOCAL_APIC for_each_clear_bit_from(i, system_vectors, NR_VECTORS) { set_bit(i, system_vectors); - set_intr_gate(i, spurious_interrupt); + entry = spurious_entries_start + 8 * (i - FIRST_SYSTEM_VECTOR); + set_intr_gate(i, entry); } #endif }